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With annuals and perennials you can have colour at any time. But annuals and perennials are not just a quick way to fill a garden with colour, they also introduce diversity with their huge range of foliage forms, textures and growth habits. Although they may be scorned because they are short lived and sometimes untidy, they are relatively cheap, easily propagated, tough, adaptable and above all, versatile. Trees and shrubs are usually permanent, which is good, but they can become staid and uninteresting, annuals and perennials brighten the garden, are a way to have continuous variety and make it easy for you to experiment until you have the effect you want. Marigolds will be out if you want pastel shades, while impatiens will be unsuitable for a dry garden, but whatever the design, there is such a wide range of annuals and perennials there's sure to be something that will fit.
Before going too far we should define the terms annual, biennial and perennial. An annual is any plant that grows from seed to full maturity within one growing season. Marigolds, ageratum and zinnias are typical annuals, they flower, set seed and die, all within a single year. Biennials, such as Canterbury bells and some foxgloves, complete the cycle over two years. Perennials are plants that live longer than two seasons so, strictly speaking, shrubs and trees are perennials. However, gardeners generally mean plants that don't develop woody when they refer to perennials.
There are several forms of perennial, some, such as Armeria, are evergreen and don't have a period of total dormancy, but very few flower continually. Herbaceous perennials generally have a period of dormancy, when they die back to a permanent rootstock. This is usually during winter, but those native to areas with hot dry summers may be dormant in summer or during periods of very low rainfall.
Some herbaceous perennials have developed the ability to use their roots or stems as food storage organs to ensure that they have a good chance of surviving extended periods of dormancy. These organs, which are known as rhizomes and tubers can often be separated from the parent plant and grown on as new plants. They function in much the same way as bulbs and corms. Examples of tubers include dahlias and alstroemerias, while bearded irises are probably the most widely grown rhizomatous plants. Some plants, such as kikuyu grass, have specialised rhizomes known as stolons, which spread across the surface of the ground, or just below the surface, taking root as they spread.
Some perennials are treated as annuals, either because they cease to be attractive as they age, or because they are incapable of surviving cold winters. Petunias and impatiens, for example, may live for several seasons if protected from frost, but they become leggy and untidy, so they are usually replaced annually.
It's common for a genus to contain both annual and perennial species, such as the annual and perennial cosmos, or species with differing growth habits, like the fibrous and tuberous rooted irises and begonias. Under garden conditions the differences between annuals and perennials, rhizomes, tubers, runners, corms and bulbs tend to become blurred. The important thing is how you use the plants, and with annuals and perennials you can give free rein to your imagination.
Climate adaptability
Annuals brighten any garden and because they are only temporary plants and always treated as such they succeed everywhere. Gardeners in cold areas can briefly ignore the prospect of winter bleakness and inject a touch of tropical colour into their gardens. The fact that annuals may be unable to reproduce successfully in your climate is unimportant. As long as they provide bright colour they will have served their purpose.
The climate adaptability is important of annuals when you want to plant for continuity. Most annuals are frost tender and must be planted in spring, after the last frosts, with a view to summer and autumn flowering. However, many can be planted in the autumn and left to over-winter for spring flowering. These plants are known as hardy annuals because they can survive the winter cold. Pansies, sweet William and Iceland poppies are among the best known hardy annuals. With careful planning it's possible to have bloom almost year round.
Perennials vary greatly in their hardiness and adaptability. Most of the traditional garden perennials are hardy and very adaptable. However, those from southern Africa, central and South America and Australia tend to be less cold tolerant and may not be suited to frosty areas, especially where late frosts can be expected.
If you live in a colder climate, say the central North Island or from Canterbury southwards, there is a way that you may be able to grow these plants. Often the problem is not so much the cold but a combination of cold and wet conditions. Plants, such as Gerbera, will tolerate quite hard frosts if they are kept dry but will rot if they are cold and wet. Most gardens have a few areas that are protected and remain dry in winter, these are the places to plant the South African daisies and the tender novelties like Alonsoa. Some tender perennials, such as Heliotrope and the 'Butterfly' impatiens demand complete frost protection. If you're happy to treat them as annuals that's fine, otherwise you'll need to either grow them in containers, so they can be moved under cover for the winter, or propagate them in the autumn and keep the small plants indoors until spring.
Annuals are also subject to all the normal climatic considerations — wind, salt spray and summer heat — but they are remarkably resilient plants that carry on flowering under most conditions. Nurseries and garden centres stock a huge range of annuals and with careful planning there should be no shortage of choice wherever you live.
Garden design
Usually you start out with some idea of how you want your garden to look. If you're keen on having a cottage garden, perennials may make up the bulk of your planting; conversely if large rose beds are your preference you may need just a few annuals as fillers. Every garden has a place for annuals and perennials and there are many ways to use them.
Think of annuals and the chances are you'll think of vivid flower beds. The massed plantings seen in botanic gardens and large private gardens are beyond most of us, but one or two beds devoted entirely to annuals do not look out of place, even in a small garden. Of course, lawns and flower beds go well together. A bowling green-like sward is offset to perfection by a bed of riotous colour and the flower beds are easy to view and walk around when surrounded by lawn.
Perennials too, are often best grown in large beds. This not only enables you to make a bold impact by planting in colour groups, it also allows the various foliage forms to be emphasised. The only disadvantage of large beds is that they can look very stark and bare in winter. Use hardy annuals, such as pansies, and the winter flowering perennials like polyanthus to brighten them in winter.
Rockeries are the ideal place for many of the small alpine perennials, such as Dianthus, Armeria and Aubrieta. These little mat or clump forming plants are undemanding and are often nearly evergreen, so they're attractive year round. Small annuals, such as Lobelia and Viscaria are not out of place in rockeries, but they must be used with discretion or they may overrun the choice plants. See the chapter on rockeries for more details.
Woodland and bog gardens would be very bare places without perennials. Bog primroses, astilbes and irises beside a trickling stream make a perfect garden scene. These are the garden styles where foliage comes to the fore; the ferny fronds of the astilbes, the huge leaves of Gunnera maculata, the variety of colour and form in the hostas and the dinner plate sized glossy, deep green leaves of the Chatham Island forget-me-not. Long after the spring flowers have gone these plants continue to delight.
If your garden is too small for any of these grand schemes or you just want portable colour, annuals and perennials are great in containers too. Hanging baskets full of trailing lobelia, petunias and begonias may be something of a cliche but they're hard to beat for colour.
Gardeners always have favourite plant and over the years certain genera have come to dominate our gardens. This sometimes leads to such plants as giant-flowered chrysanthemums, dahlias and polyanthus being regarded as 'vulgar'. In the strictest sense of the word they are, but for the very best reasons: they are great garden plants that are easily grown, colourful and reliable.
Dahlias and chrysanthemums add height and colour, and continue to flower well into autumn. Polyanthus bloom right through winter and in spring they are joined by the primroses and all their other Primula relatives. Irises are justifiably popular for their wide size range and flowering season and they go well with hostas, which are now becoming indispensable for their bold foliage and delicate flowers.
By the sea, pelargoniums dominate and their arresting colours make them superb tub and window box plants too. Marigolds (Tagetes) add the brightest yellows and golds to summer borders and petunias and daisies of all sorts abound in our gardens. Begonias come in so many styles and colours that they feature in every good garden.
As much as you may want to avoid your garden becoming clichéd, don't ignore these well tested and popular plants.
Annual flower bed
Snooty gardeners may think annual flower beds vulgar, but most of us can't fail to be impressed by the effect of all that colour and diversity in such a small space. Planned massed bedding demands a considerable amount of time and effort for a fairly brief display, and the effort has to be repeated at least twice a year. This eventually loses its novelty for all but the most dedicated gardeners; that's why really impressive flower beds tend to be restricted to botanic or corporate gardens and private show gardens.
Making a good flower bed requires that the soil be worked to a fine tilth and regularly fertilised. To keep up the colour as long as possible may mean replanting up to three times a year. The main summer display is put in around late September to early October and may be removed as early as February. It is replaced by an autumn to early winter selection that is removed in late May when the late winter to early spring selection is planted. In areas with cold winters only two plantings may be necessary; mid October for the summer display and mid to late April for late winter to spring colour.
The bold display we expect from massed annuals allows the gardener to get away with some pretty shocking colour combinations. Beds composed of many clashing colours make an immediate impact, but they can be hard to live with. Careful colour planning and consideration of height will result in a bed that is just as colourful while being far more harmonious and relaxing on the eye.
Massed bedding doesn't have to be rigidly planned, the readily available wildflower seed mixes offer an easier alternative: just scatter the seed, rake it in lightly and wait. Provided the seed bed has been well prepared and you keep the weeds down, the plants will do the rest. The seed companies have done all the colour mixing and size gradation for you, although there's nothing to stop you making up your own seed mixtures and scattering them to the wind. Quite often the effects of such random sowing are better than anything you could have planned, which just goes to show that nature is still the best gardener.
Beds of annuals are not just about flowers, some very interesting effects can be created by foliage alone. Silverleaf, bloodleaf, Coleus and many other bedding plants don't need flowers to make an impact. Others, such as Celosia and the red leaf begonias, combine interesting foliage with bright flowers.
Less ambitious gardeners can still grow flamboyant annuals without going to such great lengths. Incorporating annuals into a perennial border will help avoid the drab appearance that many perennials have late in the season. Annuals grown around shrubs achieve the same effect by extending the colour after the main spring floral display and they also act as a colourful ground cover that will smother out weeds.
A garden that combines annuals, perennials and shrubs, the 'mixed border', provides the maximum flower colour and foliage variation over the longest period. It's easy to plant out, develops quickly and grading the heights of the plants is simplified when you use annuals to fill in the gaps.
Herbaceous border
Herbaceous perennials blend well with other garden plants, especially annuals, but because they are regularly lifted and divided it's often more convenient to cultivate them separately from other plants, in large beds. Lifting the plants, dividing and composting is greatly simplified when there are no permanent shrubs or trees in the way. Because these perennial beds are often used as an edging to a lawn, driveway or wall they are usually called herbaceous borders, even when they're not really borders.
The herbaceous border requires no special construction techniques, it's just a large garden bed. It can be edged with a low hedge or some form of retainer, such as timber half-rounds or bricks, or it may just be cut from a lawn. The soil should be thoroughly prepared by digging in plenty of compost and applying supplementary fertilisers. Beds cut from lawns will benefit from a light dressing of lime, otherwise a general garden fertiliser will be adequate. Most large perennials are rapid growing and heavy feeding with fairly deep roots, the more you can do loosen up the soil so they have room to spread, the better they will grow. It's not possible to add too much compost, provided it's well rotted down.
The skill in developing a herbaceous border is in the planting. Done well it's is the peak of garden excellence, done poorly it's just an assortment of mismatched plants. Decide on an overall theme before you begin. There should be some sense of direction or emphasis, say plantings within a restricted colour range; groups of compatible foliage, such as all silver leafed plants; or plants with similar flower types, beds composed entirely of daisies for example. Remember to consider the varying heights of the plants. Obviously, if the border is against a wall, the higher plants will need to go to the back, but you must also take care that the plants don't hide one another in a jumble of foliage. By varying the heights you can highlight particular plants by exposing them or hide the less attractive parts of other plants by partially covering them.
This may seem a rather rigid way of planting, and indeed it can be. The best gardeners know when to break the rules with effects like brightly contrasting colours or foliage, and they know when to hold back too. Growing a successful herbaceous border demands that you know your plants. You won't go too far wrong with a well worked friable soil with a little general garden fertiliser added before planting.
Cottage gardens
The cottage garden aims to bring back fond reminiscences through natural randomness and plant associations. By planting simple flowers and rambling old fashioned shrubs, particularly roses and others with fragrance it's possible to create a charming effect. A cottage garden should make you want to explore; it should be filled with interesting little novelties waiting to be found. Night scented stocks, small pansies, cornflowers and larkspur are annuals that are perfect for the cottage look. Among the biennials and perennials, consider foxgloves, Coreopsis, Scabiosa, Dianthus, all the various primulas, and peonies.
If your aim is to create a garden of memories, avoid using too many plants with large double flowers and vibrant colours. If the semi-wild look is what you're after, any colour is acceptable, but once again avoid flowers that look 'overdeveloped'. Cottage and semi-wild gardens should have a light, airy feel; single flowers on rather open bushes are more appropriate than compact bushes with large double blooms.
Cottage gardens and semi-wild gardens are often promoted as an easy-care alternative, but don't be fooled, they require just as much planning as any other garden style and probably more maintenance. Planning a cottage garden depends largely on the layout of your site. Large open areas lend themselves to extensive beds and drifts of plants, the wildflower seed mixes are very useful here. If large beds don't appeal, dividing up a big garden into several small theme gardens is a good way to maintain interest. Try to design the garden so there's always something new around every corner; the prospect of a pleasant surprise keeps people looking and adds to your own pleasure. Compact gardens are usually better suited to small pockets of flowers and containers full of bright colour.
Woodland gardens
Recreating a natural effect is the prime aim of the woodland garden, and the closely associated bog garden. However, such freedom doesn't mean that you can ignore the rules: the natural look and the randomness are only apparent, not real. Creating a woodland requires just as much attention to detail as any other style, often more so because there is always the possibility of some plants running rampant and completely dominating the garden. The great paradox of gardening is that the more natural the effect the more planning it requires. However, making mistakes is one of the best ways to learn, so accept the occasional setbacks philosophically.
Of course, to have a woodland garden you must first have trees, very few woodlands are planned from scratch, they are developed to make use of the area under existing trees. First appearances may suggest that foliage dominates in the woodland garden, all those hostas and ferns, but careful study will reveal a subtle blend of foliage and flowers, and give you an idea of the proportions of the plants. Novice gardeners are inclined to think that a woodland garden must be absolutely full of plants, when in reality a better understanding of plant sizes and growth forms enables the gardener to create an illusion of abundance with relatively few plants. When you look more closely at a well-designed garden you'll find that there are really only a few main plants that immediately catch your eye, the bulk of the rest are fillers.
Another advantage of not cramming everything in is that you have room for the little treasures: those plants that you forget about for most of the year, then all of a sudden, much to your delight, they're there again. Flowers in the woodland garden tend to be concentrated around spring, but there are enough late flowering small perennials and shrubs to maintain interest. It's also acceptable to plant a few shade loving summer annuals, such as impatiens and mimulus, to add a dash of colour. However, be discreet, tranquillity is important in the woodland garden. Rockeries and bog-gardens demand a similar approach, see the later chapters for details.
Container growing
Many annuals and perennials make excellent container plants because they provide plenty of colour, yet don't take up a lot of room. Many, such as pelargoniums and Portulaca are also drought tolerant, which can be a lifesaver when you forget to water.
Use window boxes and tubs planted with vivid annuals to brighten up dark areas in summer then replace them with polyanthus and violas for winter colour. If you live in a cold area, but have a greenhouse, conservatory or covered patio, you can grow your tender perennials in containers and move them under cover for the winter.
Always use a good potting mix in your containers and remember to mix in some slow release fertiliser. Add a wetting agent too, or you may find the mix very difficult to re-wet if it dries out completely. Your potting mix will probably contain fertilisers, but regular watering leaches them; container plants demand regular feeding and liquid fertilisers are usually the most convenient to apply.
Don't be afraid to innovate and improvise, shocking colour combinations or novelty containers, such as boots and old commodes, add interest. The ways of using annuals and perennials in containers are endless; the chapter on container gardening will give you plenty of ideas.
Care and cultivation
Annuals and perennials pack a lot of growth into a short period of time, consequently they often have high nutrient demands. Working in plenty of compost and supplementary fertiliser before planting is usually best. Thorough preparation is preferable to trying to correct problems later. Additional fertilisers, as a mulch, or in organic, powdered chemical or liquid forms can be used to keep the plants growing steadily, but they can't make up for inadequate preparation. Avoid using very high nitrogen fertilisers or you may find that you get plenty of foliage but few flowers. A balanced fertiliser with a little extra potash is usually best. Some perennials, most notably the southern African daisies, prefer fairly poor soils, so yet again it pays to know your plants.
Regular watering is also important, it's no good having a rich soil if the plants are too wilted to use it. Watering annuals and perennials from above with sprinklers can damage the flowers and beat the plants down to ground. It also causes puddling, which can lead to a hard crust developing on the soil. Perforated soak hoses and drip lines are preferable, and more water-efficient too. If you must use sprinklers, choose the finest mist you can get. Containers demand regular watering, often daily in summer, and hanging baskets dry out particularly quickly.
Routine maintenance will keep your plants blooming longer. Remove any spent flowers and developing seed heads (unless you want the plants to self-sow), as once a plant sets seed it may cease flowering. Remove any damaged foliage or stems and stake tall plants, such as delphiniums. If getting the largest flowers is important, it pays to disbud plants like chrysanthemums, dahlias and tuberous begonias. This means removing the small lateral flower buds to produce larger terminal buds. You will need to consult specialist publications for the precise methods for each genus.
Provided they are kept growing steadily, annuals and perennials are remarkably free of pests and diseases. Sure, they can fall foul of all the regular pests, such as aphids, mites and various caterpillars, but these problems can usually be traced back to the growing conditions. Established plants in good growing conditions can cope with minor pests and diseases, but those in poor growing conditions will succumb. Young seedlings are far more vulnerable regardless of how good the conditions are. They are likely to be attacked by slugs, snails, cutworms, earwigs, slaters and birds, although losses from anything other than slugs and snails are seldom significant. See the pests and diseases chapter for control details. Seedlings are also prone to the fungal diseases known as damping off. Damping off rots the seed leaves and stems, causing the seedling to collapse. Good hygiene lessens the problem but damping off can occur at any time, so it's a good idea to regularly drench young seedlings with a fungicide solution.
At the end of the summer season you will need to remove the spent annuals and tidy up the dead growth on the perennials. If you intend to replant with overwintering hardy annuals remove the summer plants when they show noticeable signs of deterioration, otherwise leave them for some late colour. Getting your winter and spring annuals planted early insures they are well-established before the really cold weather arrives.
Ground cover plants
Ground covers are not just ornamental. They serve to bind the soil with their root, this stops heavy rains washing away the topsoil. By covering the surface of soil they prevent the sun drying the ground and stop the wind blowing away the topsoil. They are, in effect, living mulches.
Some ground covers, such as Dichondra, can be used as lawn substitutes while others are an easy way of adding quick colour or foliage variation. The following is a list of ground covers that are suited to a variety of purposes. Many other perennials may be used as ground covers but are not primarily grown for the purpose. For details of these plants check the sections covering shrubs, perennials, climbers and herbs.
Obtaining plants
When first establishing a perennial garden you will probably buy all of your plants from a nursery or garden centre. However, by the end of the first season you will have quite a few large plants ready for dividing. Some perennials, such as peonies, will grow for many years without needing to be divided, but most need breaking up at least every three years. Many perennials may also be grown from cuttings, refer to the propagation chapter for details.
Annuals must be raised from seed, you can do this yourself or buy ready to plant seedling punnets from a garden centre. For small quantities raising your own seed is seldom cheaper than buying seedlings, but if you have large beds to plant out, growing your own represents a considerable saving. If you need large quantities of seedlings it's best to find a nursery that will order for you from a commercial growers' seed catalogue. Not only will you make greater quantity savings this way, you'll also find that the commercial seed selection is usually better than garden centre stock in both range and quality.
Seed sowing and germination is usually very straightforward. In many cases the seed may be sown directly where it is to grow, although it is more common to sow in trays and then plant out. The only complication is timing: you don't want to sow too early as your seed may fail to germinate or the seedlings may be frost damaged, too late and they may not mature before cold stops their growth.
Bulbs
Bulbs are a highly varied group of plants that have evolved the ability to survive harsh climatic conditions by developing the food storage organs we call bulbs and corms. To most of us bulbs mean springtime; think of bulbs and we imagine large drifts of daffodils in park-like woodlands or formal beds of boldly coloured tulips, but there's much more to bulbs than the spring scene, glorious though it is. By planting a wide selection of bulbs you can have flowers throughout the year; an early spring display followed by the brilliant blue of irises, then the vivid colours of gladioli in summer garden and amaryllids with Colchicum in the autumn. In mild areas Lachenalia will flower in winter despite the short days and it's possible to have Ipheion and snowflakes in bloom well before spring in most parts of the country.
Because they are dormant for much of the year, often bursting into growth and flower over a short period, bulbs tend to have an element of surprise that is lacking in shrubs and perennials. The seemingly sudden appearance of daffodils, snowdrops and bluebells in spring is somehow more exciting than the flowering of the trees and shrubs, even though we know it's going to happen. Planting dry bulbs in autumn and seeing them flower in spring seems to reaffirm life in a way that other plants cannot match. Likewise, it's always a thrill to find Amaryllis, Colchicum, Nerine and Schizostylis bursting forth in the autumn when all other plants are signalling the onset of winter.
There are many ways to grow bulbs too. They can be planted in large drifts under trees, massed in large flower beds, dotted among small shrubs in a rockery, or carefully tended individually in pots. But however you grow them bulbs are primarily used to provide colour, relatively few are grown for their foliage. Granted the leaves of trilliums anddog violets are attractive and the spear-like foliage of the gladiolus is very distinctive, but were it not for the flowers it is very unlikely that these plants would be widely grown.
Cultivation and care
The very effective survival mechanism and the reserves of energy provided by the storage organ means that bulbs, more than any other group of temperate garden plants, continue to perform and thrive even with very little attention. However, such easy-care plants are likely to be neglected; gardeners often fail to notice when their bulbs are not performing as well as they should, simply because they are taken so much for granted. With just a little care and attention you can ensure that your bulbs continue to provide maximum enjoyment for many years.
Getting the best from your bulbs requires only that you prepare the soil before you plant them, that they receive occasional feeding and that any pests and diseases are dealt with promptly. Preparation is vital, few bulbs will tolerate very wet conditions for prolonged periods, so providing good drainage is usually the prime consideration. The easiest method of ensuring good drainage is to add extra coarse material to the soil; stone chips or coarse bark are good, as is pumice and perlite. A layer of such material beneath the bulbs will stop them rotting and allow their roots to spread quickly into the surrounding soil.
Some bulbs, most notably the Asiatic lilies, prefer acidic conditions and grow well with rhododendrons and other acid soil plants. Others, particularly tulips and irises with I. tingitana in their background, prefer slightly alkaline soils and do best with added bonemeal or dolomite lime. Most bulbs, however will grow well with a soil pH of around 6.5, and require no special fertilisers. A general garden fertiliser is all that is required to give them the nutrients they need. Apply any fertilisers at about half the recommended rate or you may find that you get very good foliage growth but few flowers. For the same reason it is better to avoid fertilisers that are high in nitrogen.
Provided the drainage is good, bulbs are not greatly troubled by diseases other than viruses, which are usually incurable and often show up as yellow flecked foliage or distorted flowers. Some viruses are relatively benign and can be tolerated, but most gradually diminish a plant's vigour to the point where it's better to replace the plant.
Many of the southern African bulbs demand dry summer conditions and perfect winter drainage: if they become too wet they soon rot. Bulbs that are forced into flower out of season may also rot if kept too wet. However, if you restrict yourself to growing hardy bulbs outdoors, it's very unlikely that diseases will cause many problems.
The greatest pest of bulbs is the narcissus bulb fly. The larvae of this small fly burrow into the flesh of daffodils and related bulbs and gradually eat away at the bulb. Before long the bulb is severely damaged and eventually all that is left is a dried husk. Bulbs will often continue to grow and flower despite fly damage, but they are usually stunted and distorted. Careful inspection and soaking in an insecticide solution before planting are the best ways to avoid this problem. Plants that are very prone to bulb fly will have to be sprayed during the growing season; use a systemic spray to ensure that the entire plant is treated. Other burrowing pests, such as wireworms and millipedes, also damage bulbs, while slugs, snails and cutworms feed on the foliage. Aphids are also common pests and frequently occur in large numbers on tulips. The damage caused by the chewing and rasping pests can often be tolerated, but sucking insects, such as aphids, may spread virus diseases and should be kept under control.
The differences between bulbs and corms?
Bulbs and corms appear similar to one another, but differ in their internal structure. While these differences are not very important in terms of cultivation there are special methods of propagation for each type.
True bulbs produce foliage and roots from a flattened area at the base of the bulb, known as the basal-plate. There are two types of true bulbs, tunicate and scaly, which are differentiated by the way their tissue layers, or scales, are arranged. Tunicate bulbs, such as onions, have a papery outer skin and scales arranged in concentric rings that radiate from the centre of the bulb. Tunicate bulbs can be tricky to propagate and are often best left to multiply naturally rather than being forced in any way. Scaly bulbs, such as lilies, have overlapping scales, a bit like fish scales, that are usually arranged in a spiral pattern radiating from the centre of the bulb like so many staves on a multi-layered barrel. Each scale is easily detached, so propagation is just a matter of removing scales and growing them on.
The foliage of corms develops from growth eyes on the top of the bulb, not from the basal plate where the roots develop. As the corm often has several growth eyes, it is possible to propagate corms by cutting them up. This, however, is not a popular method and is largely unnecessary as most corms produce masses of small cormlets that may be lifted at the end of the growing season.
Bulbs in your garden
The traditional ways of growing bulbs are by concentrating them in large beds or using them as underplanting in shrubberies or woodland areas. However, as in all areas of gardening, don't be afraid to experiment. Many of the smaller bulbs are superb in rockeries and can be used to create drifts of colour, among the best are Chionodoxa luciliae, Iris reticulata and Ipheion uniflora. Some of the southern African bulbs, such as LachenaliaHaemanthus, Scadoxus and Veltheimia are very much at home in succulent gardens.
Bulb boxes and raised beds
Growing bulbs in raised beds eliminates the risk of poor drainage and also makes it easy to lift the bulbs without having to disturb other plants. Such beds are also natural focal points that are sure to attract attention, which is an advantage when the bulbs are flowering and looking their best, but it does mean that as they die off something has to be done to hide their untidy appearance. This is not so much of a problem with plants like gladioli, the planting of which can be staggered to provide a continuous display, but spring bulbs tend to all finish within a few weeks of one another. The best solution is usually to plant fast growing annuals, such as petunias, to hide the browning bulb foliage.
Make your boxes at least 30 cm deep and build the soil up in layers. Use coarse gravel chips for the bottom layer to ensure good drainage. Next, add a humus layer of compost, potting mix or peat, this should be equal to about 1/3 of the depth of the box. The bulbs should be planted in this layer; the neck of the bulb level with the top of the compost. Top off the box with a 4–15 cm depth of gritty soil mix that allows water to drain away from the surface. The exact depth of this layer depend on the bulbs being grown, some require deeper cover than others. For example, gladioli should be planted at least 100 mm deep, while amaryllids prefer to be planted near the surface.
Woodlands
Many bulbs do extremely well under woodland conditions and some may naturalise. Lightly foliaged deciduous trees, such as Japanese maples and dogwoods, are the best cover for woodland bulbs as they provide a regular and natural mulch and only light shade. Provided the soil is not extremely acid or alkaline, establishing woodland bulbs requires little effort other than planting and occasional light feeding. This type of garden is often ultimately the most satisfying as it provides a cool natural setting, is appealing to gardeners and wildlife alike and requires little maintenance once the initial weed problems have been brought under control. The woodland bulbs, such as Cyclamen, Trillium and the wood anemones don't have the flamboyance of hybrid tulips, gladioli and daffodils, but their charms are more subtle and tend to be longer lasting.
Bulbs in containers
Spring bulbs in particularly are well suited to container cultivation and growing them this way makes them portable, which has several advantages.
It widens the range of bulbs that you can grow by allowing more tender bulbs to be grown under cover.
You can move spent bulbs out of view as they start to dry off rather than having to try to hide them with other plants.
Container growing is a good way to create colour for paved areas, such as courtyards, or anywhere else that gardening in the soil is not practical. Small bulbs do well in window boxes.
Fussier species, such as Haemanthus, can be given the individual attention they require when grown in containers.
The bulbs can be lifted or dried off without disturbing other plants.
Hardy bulbs can be potted, then moved to a sheltered area for forcing into flower.
Hyacinths, irises and the shorter varieties of daffodil make good subjects for forcing. Plant them in a bowl in early autumn and bury the container so that the rim is level with or just below the soil surface. Mound the soil over the container so the bulbs are slightly deeper than normal and make sure the container is clearly marked; they're easily lost in a crowded garden.
Lift the container in early winter and gently remove the excess soil to expose the growth shoots, which should be clearly visible. Place the container indoors in a bright position that remains at a steady cool temperature. As the flowers start to develop the container may be moved to a warmer position but excessive heat or lack of humidity will shorten the flower display.
When planting in pots of other containers make up a soil mix similar to that described for boxes: a coarse drainage base, a moisture retentive middle layer and a free draining top layer. Add a little general fertiliser too so that the bulbs get a good start. Plant your bulbs so that each has room to expand as it grows. Don't be stingy, they need to be massed to create a lasting effect, but don't pack them in so tight that they have to compete for space, moisture and nutrients. Covering about half the available surface with bulbs is a good rule for most genera.
Bulbs in grass
The typical picture-postcard scene of daffodils, bluebells, crocuses, snowdrops and other spring bulbs growing in grass in the shade of flowering cherry trees is not too hard to recreate. Bulbs generally do well in such a situation and can be left undisturbed for years.
The main problem is knowing when it's safe to mow the grass. There's no possibility of close mowing, so you have to forget about having a good lawn; the idea is that the area is treated more like a meadow. Don't attempt to mow the grass while the foliage of the bulbs is still green. It's important that the foliage be left to die off naturally because, like any other plants, bulbs depend on their foliage to photosynthesise the starches and sugars they need to survive. The foliage doesn't need to be completely dried off before mowing, provided the bulbs have been well-fed, but there should be no more than about 2 cm of green stem remaining. Cutting off green foliage will certainly have an adverse effect on the following season's flowering and may shorten the life of the bulbs.
Precisely when you will be able to mow depend on the selection of bulbs and the type of grass. Early flowering bulbs, such as snowdrops and daffodils, generally dry off quickly after flowering, which will allow mowing by middle of December in most areas. Regardless of this you should choose a fairly short grass, such as a variety of fescue, that won't overwhelm the bulbs or require too much mowing. You may also wish to have some autumn-flowering bulbs, such as autumn crocus (Colchicum) and Sternbergia, but these pose problems as you will be unable to mow from about late January onwards. By planting autumn flowering bulbs in large clumps or near the base of trees or in other clearly defined areas they should be obvious enough that you can mow around them.
Rockeries
Rockeries, more than most other garden styles, attempt to recreate natural features in the garden and as is so often the case, the more natural and simple the finished product appears the more difficult it is to create. It should therefore come as no surprise that rockeries are one of the most difficult areas of garden design. Indeed, they are often viewed as the height of the gardeners' art.
The secret of that art lies in creating a sense of scale. The plants must be in proportion with size of the rocks and the garden as a whole. A large rock garden with sizeable rocks allows larger plants to be used while still maintaining a sense of proportion, while creating a successful small rockery demands more skill in order to maintain realistic proportions. It requires a knowledgeable gardener with an artistic touch.
Before building your rock garden, visit some of the natural rockeries that can be found in the hills and mountains. Look at how time and the forces of nature have acted on the rocks. In stable areas where the rocks have settled and plants have started to grow, you will usually find that the rocks are well embedded and their grain tends to run in the same direction. Jumbled piles of loose rocks are unstable, liable to move and few plants will be found there. The screes that are so common in the South Island mountains are so prone to movement that the plants that grow on them have many unique features which enable them to survive in such a harsh environment. Keep these natural variations in mind when designing your rockery and you will be able to create changes of mood in the design and will also be better able to cater for the particular needs of the plants.
Rockeries are all about slopes and changes in level, so they are an excellent way of developing a naturally sloping site. On flat ground there are no natural slopes and positioning the rockery becomes critical. A small rockery in the middle of a flat expanse of lawn is bound to look unnatural. Flat sites require large rocks or extensive contouring to provide the necessary variations in level.
Large rocks need to be sunk into the ground to stabilise them and to create a natural effect — work on the iceberg principle: 9/10 is underwater, or in this case underground. The excavation required for this will often provide enough topsoil to raise other parts of the garden. Excavating a pond and surrounding it with large rocks is another way to emphasise changes of level.
Rocks
You can use any rocks for a rockery — bigger is better — but stick to just one type. Nature's rockeries show very little variation in texture and colour, and combining widely differing rock types is sure to look artificial and it also draws attention away from the plants.
The rocks can vary widely in size, which is quite natural, but the design should be based on large foundation rocks that are at least the size of a decent boulder. Too many small rocks and the rockery begins to look like a quarry.
Large rocks can also be used in garden beds and are particularly effective as islands in large expanses of ground cover.
Construction
Before building the rockery check the drainage. If water does tend to lie in certain areas you could excavate them and refill with shingle, which will look quite natural, but in severe cases PVC drainage pipes may be required. Naturally low-lying areas may be suitable for a rockery pond.
A rockery must be solidly built because you will need to be able to stand on the rocks when planting and weeding. If the slopes are severe the rocks will need to be well embedded to ensure that they are safe and able to retain the soil. Terracing is one way to make a stable foundation on a sloping site but it often looks unnatural.
Start your construction at the lowest point of the rockery, using the largest and heaviest rocks. Set the rocks with their broadest, most stable section at the base and keep the grain running the same way. Positioning rocks on their ends or sides is bound to create instability. Large boulders can be positioned as separate islands, but in the main you should work upwards in layers, with each layer gently sloped back and down. Any gaps between the rocks should be filled with gritty soil or fine gravel, taking care to eliminate any air pockets that would be an ideal home for slugs and snails.
Soil
Garden topsoil is generally too heavy and packs down too hard for rockeries, although it can be used as the basis for a soil mix. The perfect rockery soil is a mixture of high-humus compost and fine shingle chips. A 1/3 each by volume mixture of good loamy topsoil, leaf mould or compost and fine shingle chips makes a soil that is light and free-draining yet moisture retentive. Bark-based potting mixes with added shingle also make excellent rockery soils.
Large areas of soil in the rockery should be topped with a mulch of shingle chips. This retains moisture and, provided you stick to grey or tan gravel, it looks very natural. Bark chips could be used instead but they do tend to appear somewhat out of place in an alpine scene.
Extra shingle can be added to the soil mix to simulate natural scree. Creating a scree slope is a good way to make a smooth transition between two large rocks with a considerable height difference. Start with a layer of large rock chips — these hold the slope in place and should be firmly rammed into place — then add up to 15 cm of soil and top it off the soil with 15 cm of your scree mix. When you plant in the scree, some of the soil should be mixed with shingle to ensure the plants have adequate moisture, but it is important to have a good depth of shingle to create perfect drainage and lessen the potential for weed growth.
Planting
Use plants that are compatible in style and growth habit, and don't overplant. Remember those natural rockeries? Natural rock outcrops have far fewer plants than most rockeries. The structure of the rock often captures your attention before the plants are even noticed and this is also a feature of the best garden rockeries. An overplanted rockery tends to look like a herbaceous border with rocks.
Rather than pack your rockery with plants you can make it interesting by choosing plants that are out of the ordinary. A rockery should be a garden of little treasures waiting to be discovered so that the more you look the more you see.
Maintenance
Rockeries require regular watering in summer and you need to be careful as it is very easy to wash the soil away. Use a very gentle spray or a perforated soak hose, which allows the moisture to seep in gently without creating any rivulets that will erode the soil.
Weeding can be difficult in rockeries and at all stages of the construction and planting you need to think about creating access. A few flat stones positioned for use as stepping stones will help greatly. Also be careful when positioning ponds; it's all too easy to site the pond hard up against a large rock only to find that you no longer have access to the far side of the pond, which is sure to be where the weeds grow.
Rockery alternatives
If you don't have the room for a rockery or if the whole idea just seems too much to cope with, you can still grow rockery plants. Garden centres often sell large troughs made out of a porous peat and concrete mixture called tufa. When filled with coarse gravelly potting mix these troughs are ideal for cultivating alpines and rockery plants.
Many rockery plants will also happily grow in the gaps between paving stones. You can even leave out the odd stone and create small pockets of special soil especially for this purpose.
However you grow them, rockery and alpine plants include some of the most intriguing and charming garden beauties. Successfully cultivating them in a natural-looking rockery is one of the most satisfying forms of gardening there is.
Herb gardens
The modern herb garden is the direct descendent of the apothecary's garden. However many of the more colourful uses have passed into the realm of folklore. These days we're more likely to grow plants such as Filipendula and paeony for their beauty rather than for medicinal uses yet the value of a well-stocked herb garden is beyond dispute.
The emphasis in most modern herb gardens has shifted to the culinary herbs. There is, no doubt, an increasing interest in the medical and pharmaceutical value of herbs but by far the majority of herbs are sold for culinary use.
What is a Herb?
This question is bound to crop up in any discussion about herb gardens. The answer is, I'm afraid, fairly vague. The botanical definition is the same as that for a herbaceous perennial but in the gardening sense a herb is any plant that is commonly used for culinary, medical, pharmaceutical or cosmetic purposes.
That covers an extremely diverse range of plants many of which you would certainly not contemplate growing in your herb garden. Plants ranging from seaweed (carrageen) to the cinchona tree (quinine) fit this definition but the plants grown in domestic herb gardens tend to be culinary herbs, such as parsley and sage, or aromatic herbs, such as lavender. Keen herb growers will probably also have a few medicinal herbs, such as feverfew (Tanacetum parthenium) and Verbascum. Many common ornamental perennials also fit this definition although they are seldom used for anything other than decorative purposes.
Preparing a herb garden
In general you should prepare the site just as you would a perennial border. Work in plenty of humus containing material and give an all over dressing of a general purpose fertiliser. However, your exact method of preparation depends entirely on what you intend to grow.
The ideal herb garden will need to be able to provide a wide range of conditions to cover the wide range of plants that can be grown. There are herbs for all positions from shade (parsley and most mints) to full sun but the majority of herbs do best where they receive at least half a day's sun. Most herbs, especially rosemary, lavender and the chamomiles, need good drainage. Some, particularly those of Mediterranean origin, do best on light shingly soils while others, such as watercress, prefer boggy conditions.
Many herbs make effective additions to perennial borders and are often well worth growing for their ornamental merits alone. Others make useful container plants. Some, such as the carpeting thymes, can be used as ground covers or even lawn substitutes. Indeed if you put your mind to it there's a herb for just about every purpose.
Ponds and bog gardens
The ripples on the water surface or the gentle trickle of a stream combine movement with tranquillity in a way that plants alone cannot. It has been said that no garden is complete without an area of water yet this important garden feature is often overlooked.
A garden pond doesn't have to be a stagnant swamp. Modern plumbing methods and miniaturised pumps make it easy to have flowing water. But be careful when designing a waterfall, stream or tiered ponds, it's all too easy to descend into kitsch. The best technique is to keep everything as natural and understated as possible. Take the time to look at some natural watercourses. Notice how gently a stream curves but how abruptly water can change levels while still maintaining a smooth flow. Following nature's design guide simplifies the creation of a realistic effect.
The alternative is to make a formal pond. These usually have a geometric design and no attempt is made to make the construction appear natural. Formal ponds are nearly always built of permanent materials, usually a foundation of concrete blocks with a cement coating. Be careful with formal ponds, it's all too easy to overdo grotesque statuary and fountains. It may have been suitable for Louis XIV but a Versailles water garden looks out of place in most suburbs.
As outlined in the planing chapter the key to a successful pond is maintaining a balance between the nutrients in the water and the plant and animal life that the pond supports. It is very rare that the water in a garden pond is so lacking in nutrients that it can't support aquatic plants, but water choked with algae because it is too rich in nutrients is common.
You will either need to have a pump to keep the water circulating or add aquatic plants to maintain the balance. Although it is possible to plant directly in soil on the pond bottom, such a large area of nutrient-rich soil is bound to create initial algal growth. Often it is preferable to plant your aquatics in containers as this reduces the volume of soil in the pond and makes the plants easier to lift for maintenance. Nurseries, garden centres and pet shops that stock aquatic plants usually have discretely coloured plastic planting baskets in various sizes.
Aquatic plants come in three basic types: floating plants, such as the pond ferns (Azolla), which survive on nutrients extracted from the water; those with have floating leaves and roots that are anchored to the pond bed, such as water lilies (Nymphaea); and the fully submerged plants, such as water milfoil (Myriophyllum), with foliage that remains below the surface.
Most aquatic plants don't require a great depth of water; large water lilies do best with about 50 cm depth and pygmy lilies will grow well in as little as 20 cm of water. Ideally the depth should gradually decrease at the margins of the pond to allow for a natural transition from water to marginal to bog plants. This creates a more natural effect than a stark edge and is also better for wildlife like birds and frogs that prefer an area of shallow water. For the most natural effect your pond should be large enough to allow for this kind of graduated planting.
Considering the emphasis we have placed on good drainage, the idea of a bog garden can seem to be almost a contradiction in terms. But the bog garden is a special case and its use doesn't have to be restricted to the edge of a pond. Many gardens have areas that are just not practical to drain because the water table is very high or they are prone to flooding. Such wet patches shouldn't be considered eyesores but the opportunity to create something wonderful — a bog garden.
Bog garden plants are mainly perennials and they cover a wide range of sizes and styles. The area you have to work with will largely dictate your choice of plants. Large gardens may have room for the giant rhubarb-like leaves of Gunnera maculata and the rapid growth of the various Rodgersia, Aruncus and Filipendula species. However, many gardens cannot cope with such large plants, in which case the likes of bog primroses, Darmera peltata and the many Astilbe species and cultivars will be better suited.
The degree of wetness and the how much it varies will also influence your plant selection. Extreme variations of moisture level, such as may be experienced along a streamside can be difficult to cope with. In such cases it is usually best to construct a stone or timber retaining wall up to the presumed high-water level and build the garden above that level. Alternatively the stream can be edged with plants that are able to tolerate the changes in water level. The sedges, Japanese and Siberian irises are good choices. For smaller areas try Mimulus, marsh marigolds (Caltha and Ranunculus) and the skunk cabbages (Lysichiton).
As you move away from the water's edge the conditions become more like a perennial or woodland garden. The transition moves from bog plants to the perennials that will tolerate brief periods of wet soil, such as hostas, ferns, Thalictrum and Pulmonaria.
Consider the growth habit, flowering season, colour and foliage type when arranging your plants. Although it is usually best to grade the plants on the basis of size, you may find that you also have to consider shading and growing season. For example, it's possible to grow bog primroses with Gunnera because the primroses have usually finished flowering before the large leaves of the Gunnera shade them out. Astilbes, however, would be unsuitable because they could not tolerate the deep shade cast by the Gunnera leaves.
Most bog plants are spring flowering and by late November the flower display is largely over. However, bog plants display a wealth of different foliage types and that's where their true beauty often lies. Aim for a varied blend of foliage rather than a huge variety of flowers. The subtle variations of colour and texture between the foliage of rodgersias, hostas, bog primroses and irises create at least as much interest as their flowers and the effect is longer lasting.
Many bog garden plants prefer shade and are at their best in the light shade cast by deciduous trees, which is why a bog garden blends so well with a woodland garden. The art of the bog garden lies in perfecting the gentle transition from trilliums and wood anemones to hostas and ferns and on to the real moisture lovers like bog primroses, then finally to the irises and the true aquatic plants. A bog garden typifies all that is best in gardening with perennials; it offers the colour of spring flowers, the lushness and variety of foliage, and the interest of a wide range of growth forms.
Plant selection
The range of annuals, perennials and bulbs is enormous, and it becomes larger with every passing season. No book of this size could cover all the genera and cultivars and advances in plant breeding mean that information rapidly becomes outdated. The plants listed here are the ones that you'll find in any garden centre. Many of them, particularly the annuals, are available in a wide range of hybrid and selected forms; this list includes only the most widely grown forms and is intended as a general outline only.
Each genus name is followed by an A, B, P or B to indicate whether the plant is annual, biennial, perennial or a bulb. Those also marked with an H have herbal uses, G indicates a ground-cover plant, and R a rockery plant. The sizes given refer to height by width, eg 30 cm × 50 cm means 30 cm high × 50 cm wide.
All annuals and biennials must be raised from seed, so propagation is mentioned only in relation to perennials or the perennial species of composite genera.
Acanthus (P)
Bear's breeches (Acanthus mollis) is a tough adaptable plant mainly grown for its bold, deeply lobed, glossy foliage. Somewhat invasive, it should not be used in small gardens or narrow borders. It grows to 60 cm × 1.2 m with flower spikes up to 1.5 m. Acanthus grows in full sun if moist, but at its best in light shade. Propagate by seed, division or root cuttings. A. spinosus is similar, but has sharply lobed foliage.
Achillea (P)
The yarrows come in a variety of styles and forms. One of the most popular cultivars 'The Pearl' is scarcely identifiable as a form of yarrow but most have the ferny foliage and flat flower heads reminiscent of the well known roadside weed. The 'Summer Pastels' series has become popular for summer bedding but most yarrows are used in perennial borders. Easily grown in any sunny position. Sizes range from 25 cm x 40 cm for the 'Summer Pastels' up to 1.6 m x 1.2 m for the larger cultivars, such as the A. filipendula forms. Propagate by seed or division.
Aconitum (P)
The common 'Monkshood' (Aconitum napellus) is a close relative of the delphiniums. Mainly autumn flowering this genus is useful because its bright blue flowers and late blooming season. Also available in a pink and white forms. Prefers a moist soil enriched with extra humus. Grows in sun to moderate shade. Propagate by seed or division. Up to 1.4 m high x 80 cm wide.
Acorus (P) — G
A tough perennial for moist positions. Grass-like appearance but actually a small lily. The variegated form is good for foliage contrast.
Adonis (P) — R
Adonis armuriensis has fern-like leaves that begin to unfurl from late July and by mid August the first large yellow buttercup-like flowers start to open. Adonis isbest in cool, moist soil in light shade. It grows to 30 cm × 40 cm and is usually propagated by division.
Aethionema (P) — G, R
These perennial-like sub-shrubs usually have silvery grey foliage and heads of small pink flowers in late spring. They grow to about 20 cm × 30 cm and prefer well-drained gritty soil in sun. Propagate the species by seed and hybrids by small cuttings or self rooted layers.
Agapanthus (B)
A genus of 10 species from southern Africa. The common species, A. praecox, is a large clump-forming near-evergreen plant with long strappy leaves and clusters of 75 mm long lily-like flowers that are carried in heads at the top of tall stems. The typical flower colour is bright purplish blue, but there are white and pink forms and some very dark purples, such as 'Stormcloud'. Established clumps may have flowers at any time; late spring to early autumn is the main season. The sizes vary too, ranging from the dwarf 'Peter Pan' at 50 cm × 50 cm to large forms that may reach 1.8 m × 1.8 m. The dwarf variegated cultivar 'Tinkerbell' is a superb small rockery plant. The many forms of Agapanthus are all tough adaptable plants that can be relied upon to make a good show under most conditions. It is best sited in a sunny position, but will tolerate semi-shade. Propagate by splitting established clumps, which is best done in early spring.
Agastache (P) — H
Anise hyssop (A. anethiodora) is a soft stemmed perennial that is often treated as an annual. It is primarily grown for the ornamental value of its purple flower spikes. The aniseed flavoured foliage can be used to make a herbal tea or as a flavouring. Easily grown in any sunny position. May be raised from seed or semi-ripe cuttings.
Ageratum (A)
The blue ageratum is a very popular summer bedding plant. It forms 25 cm × 25 cm clumps with fluffy flowers in an unusual dusky-blue that blends effectively with many other bedding plants. Pink and white forms are also available.
Ajuga (P) — G
Many different foliage forms of A. reptans are available. It is a tough ground cover that grows to about 10 cm × 60 cm with spikes of purplish blue flowers. Ajuga grows in the sun or shade and most cultivars will spread rapidly if left unchecked. A. genevensis and A. pyrimidalis are non-invasive species, they are taller but have similar purplish blue flowers. All are easily grown from cuttings or self-rooted layers.
Alcea (B) — H
Hollyhocks have enjoyed a resurgence in popularity in recent years coinciding with the trend towards cottage gardens. They are available in almost any colour, but apart from the fancy double strains they are usually sold in mixed-colour packs. They are useful for adding height and colour at the back of a border and their sizes range from the 60 cm 'Majorette' through to the 1.8 m high 'Chater's Doubles'. Hollyhocks are easily grown in any sunny, well-drained position, although they usually need staking to prevent wind damage and are often attacked by rust.
Alchemilla (P)
Lady's mantle (A. mollis) has unusual light green leaves and small loose spikes of yellowish green flowers. It may is usually about 50 cm × 80 cm, but may spread rapidly in loose soils. A. alpina is very like a quarter-sized A. mollis, A. glabra is another small species. After flowering they may become untidy, but in spring and early summer they are very appealing. The flowers last well when cut. Grow from seed or divisions.
Allium (B) — H
The ornamental onions are very popular in British gardens but not widely grown here. Some, such as the yellow A. moly, are quite attractive and all are hardy but they lack the flamboyance we tend to associate with late spring and summer bulbs. Some of the smaller species, such as A. carolinianum, are suitable for rockeries. Size varies but most of the ornamentals are about the size of a clump of chives (A. schoenoprasum), some, such as A. bodianum, have broad strappy leaves but they are easily damaged and often prematurely dry and brown at the tips. Grow in light well drained soil in sun or very light shade. Some may require alpine house treatment. Propagate by seed or the division of well established clumps.
Alonsoa (P)
Alonsoa warscewiczii grows to about 60 cm × 60 cm and is very showy in flower, but short-lived and rather frost tender. A clump forming plant with small bright green leaves on wiry stems topped with heads of small flowers mainly in shades of pink and orange. Raise from seed (it often self sows) or cuttings.
Aloysia (P) — H
Lemon verbena (A. triphylla) is a deciduous shrub with leaves that are strongly citrus scented. It is often an untidy bush but regular pinching back will help to keep it compact. The spikes of lavender flowers are not very attractive. Used to make a herbal tea or pot pourri. Best grown in moist well-drained soil in sun or light shade.
Alstroemeria (P)
The Peruvian lilies are very popular and they are easily grown in most soils provided they receive about half a day's sun. The cut flower hybrids are usually quite restrained growers. However, be wary of planting some of the species; A. aurea (aurantiaca) and A psittacina (pulchella) in particular can be invasive in light soils. Most alstroemerias are around 50 cm × 50 cm. Propagate by seed or division.
Amaranthus (A)
'Love Lies Bleeding' was once a very popular annual but is now less common. Although usually treated as annuals they may live for two years or more in mild areas and eventually become quite substantial plants. The most common species are A. caudatus and A tricolor ('Joseph's Coat). Easily grown in a warm moist position. Do not plant until frost danger is past. Up to 1 m high x 1 m wide. Propagate from seed.
Amaryllis (P)
The most familiar species of this genus of bulbs is A. belladonna, often called 'Naked Ladies'. An unusual feature of this plant is that it flowers before the foliage develops. Plants from areas with pronounced dry seasons often have this characteristic which ensures that the stored energy of the bulb is directed into reproduction rather than foliage development should the rains fail.
The 50-60 cm stems appear in the early autumn and are topped by clusters of bright pink trumpet shaped flowers. White forms and various shades of pink are available. The long strappy leaves start to develop as the flowers open. Plant with the neck of the bulb at, just above the soil surface in light well drained soil. Grows best in sun but will tolerate shade from deciduous trees that will allow light through to the foliage in winter. Propagate by seed or the division of established clumps.
The bulbs with very large trumpet shaped blooms commonly called amaryllis belong in the genus Hippeastrum.
Anchusa (P)
Several species and forms are grown ranging from small bedding varieties that are treated as annuals through to the larger A. azurea forms, such as 'Loddon Royalist', which may reach 1.5 m high. Most anchusas have deep blue flowers. Plants are easily grown in any sunny position. Propagate by seed or division.
Andropogon (P) — H
Lemon grass (A. nardus formerly Cymbopogon citratus) is widely grown as a culinary herb. The foliage has a strong lemon scent and flavour. It is also good source of vitamin A and herbalists recommend it for stomach and liver complaints. The lower potion of the foliage stem is the part used. A tropical plant that demands even moisture and warm temperatures to grow well. Usually treated as a summer annual in all but the mildest areas. may be grown indoors but the flavour is a pale imitation of that of an outdoor cultivated plant. Raise from seed or divide established clumps.
Androsace (P) — R
A genus of small rock plants seldom growing larger than 10 cm high x 20 cm wide. One of the classic rockery genera. Not spectacular but appealing nonetheless. Most species have light green or silvery grey foliage topped with small white or pink flowers in spring. Best in sunny well drained scree or rockery conditions. Some may require alpine house conditions in areas subject to heavy winter rains. Propagate by seed, cuttings or self rooted layers.
Anemone (P)
The familiar bedding anemones, such as those of the 'St Brigid' strain are the most fancy and gaudy forms, grown mainly for a bright splash of colour. There are many other species and hybrids that vary greatly in growth habit and flowering season. The wood anemones, such as A. nemerosa and A. blanda, are very attractive small plants that herald the arrival of spring with their purple, pink or white flowers. They form 15 cm × 40 cm clumps. The Japanese anemone, A. huphensis (japonica), which has pink or white flowers on 1 m stems, blooms in the late summer and autumn.. It may become invasive in favoured locations. Most anemones prefer light shade and a soil high in humus. Propagate by seed or division.
Anethum (A) — H
Dill (A. graveolens) is a culinary herb that is widely used in fish dishes. It is annual that often self-sows. The stiff upright stems with heads of small yellow flowers are not unattractive but they are somewhat weedy. The foliage is best use before flowering.
Anigozanthus (P)
The Australian 'Kangaroo Paw' was touted as a potential export cut flower but doesn't seem to have been a huge success. This is possibly because the plants are not always easy to grow. They often succumb to ink spot fungus; this disease causes black patches on the foliage which eventually withers and dies. Careful attention to drainage and good ventilation will help prevent this disease occurring.
Over the years a number of cultivars have been introduced. These have mainly been hybrids of A. flavidus and A. manglesii. The colour range now extends from pale yellow through orange to deep red. As with many plants from dry areas Anigozanthus will tolerate more cold if kept dry over winter, nevertheless exposure to temperatures below -5° C will usually cause damage.
Anthemis (A & P) — H
'Roman Chamomile' (A. nobilis) and 'Dyer's Chamomile' (A. tinctoria) are the most commonly grown plants of this genus. Both are perennials with daisy-like flowers and ferny foliage. 'Roman Chamomile' is often used to make herbal lawns and herbal teas. 'Dyer's Chamomile' is used to produce a yellow dye. Very easily grown in any sunny position. Raise from seed or small cuttings. The non flowering 'Treneague' must be vegetatively propagated.
Antirrhinum (A)
Snapdragons may be grown year round in most areas. In mild climates they flower throughout the year while where winters are cold they start to bloom with the first warm days. Antirrhinums grow in most soils and will naturalise in cottage gardens. They are undemanding plants but are often damaged by rust; new strains are rust-resistant. Snapdragons are available in various sizes, ranging from 'Floral Showers' and 'Pixie' at about 20 cm high to 'Madame Butterfly', which may reach 80 cm high; some have the traditional snapping flowers but the doubles do not.
Anthricus (A) — H
Chervil (A. cerfolium) is an annual with fine ferny leaves and heads of small white flowers that is primarily used as a culinary herb. Grown from seed. Its foliage does not remain in good condition for long but sowing at regular intervals will ensure a steady supply of fresh leaves.
Aquilegia (P)
Most of the common aquilegias are hybrids of A. vulgaris, but there are some very attractive dwarf species, such as A. alpina and A. flabellata. Best in moist semi-shade with humus enriched soil. The large forms grow to about 75 cm × 50 cm, while the dwarfs are 25 cm × 20 cm. Aquilegias are graceful plants and are available in many different colours; many are multi-coloured, often in pastel tones with very subtle shading. Propagate by seed or division, aquilegias often self sow and unusual forms may pop up of their own accord.
Arabis (B or P) — G
Rock cress is a great filler for rockeries and small perennial borders. Masses of small flowers smother these plants in spring. Most are low rosette forming plants or ground covers. A. caucasica (albida), particularly the cultivar 'Snowdrop' is probably the neatest; the other species tend to become very straggly with age. In any case Arabis is not a long term perennial. Best in full sun in quite poor soil. Grow from seed or selected forms from cuttings.
Arctostaphylos (P) — G
The ground cover species A. nevadensis can be a frustratingly slow spreader but given time it covers a large area. Attractive pale pink bell like flowers and small deep green leathery leaves are attractive.
Arctotis (P) — G
These reliable heavy flowering perennial daisies are most at home in coastal conditions and can often be seen in large drifts in seaside gardens. The colours are usually very bold, although some attractive creams and pastels are available. They are slightly frost tender but will withstand considerable cold if kept dry. They grow to 20cm high × 50 cm wide. Plant Arctotis in light, well-drained soil and full sun. May be grown from seed, divisions or self rooted layers.
Argyranthemum (P)
The marguerite daisies, formerly known as Chrysanthemum frutescens, now appear under this name. They are somewhat frost tender perennials that are easily grown in any sunny position. Marguerites are great coastal plants and can be seen growing wild in many areas, particularly Sumner, near Christchurch, where wild forms have hybridised with cut-flower varieties from nearby nurseries. There are many cultivars that range from dwarf bushes to large shrubs. Colours include shades of pink, yellow, cream and white; and the flowers may be single, double or anemone form (crested). New cultivars are regularly introduced, 'California Gold' being one of the best recent introductions. They may be propagated by seed, which often self sows, but the best forms should be perpetuated by cuttings.
Arisarum (B)
The mouse plant (A. proboscideum) is the best known and most widely grown member of this genus of small Arum relatives from southern Europe. It is a little plant (12 cm × 50 cm) that is fascinating because of the way the white and brown flowers resemble small mice disappearing into the clump of dark green foliage. It blooms in spring and early summer. Mouse plant is very easily grown in any moist, humus enriched soil in shade or partial shade and may become slightly invasive. Friar's cowl (A. vulgare) is similar but it is a larger plant and its flowers are usually held above the foliage, which dies off quite quickly after the spring flowers finish.
Armeria (P)
Armeria (Thrift) is a genus of clump forming plants with tufted grassy foliage and pink or white chive-like flowers. They will grow in any position that gets a few hours sun. The most common species is A. maritima but several others, such as A. pseudoarmeria and A. latifolia, are widely grown. Dwarf forms are about 20 cm × 20 cm in flower, while larger forms may reach 40 cm × 30 cm. Propagate by seed or division.
Armoracia (P) — H
Horseradish (A. rusticana) is an extremely vigorous perennial that even the most dedicated devotees of horseradish source should think twice about before introducing into their gardens. It has long bright green lanceolate leaves and small white flowers. The tough white roots are used to prepare the well-known condiment. Very easily grown in any soil in sun or light shade. Propagate by dividing an established clump, however, this is seldom necessary as once you have it you have it for life.
Arnica (P) — H
A. montana
is an extremely potent perennial herb that was once extensively used as an internal medicine. It is now regarded as being too dangerous to use internally without supervision but is still used externally in the treatment of bruises and inflammations. It has soft green stems and bright green lanceolate leaves. The yellow daisy-like flowers appear in summer. Grow in moist well-drained soil in sun or light shade. Raise from seed or divide established clumps in late winter or early spring.
Artemisia (P) — H
There are many species of Artemisia and they are quite variable. Most are bulky upright bushes grown for their silver grey foliage but A. lactiflora is a rosette forming ground cover most notable for its white flowers while A. schmidtiana has fine, almost hair-like foliage. Most prefer to grow in hot sunny locations (A. lactiflora is an exception) and do best in a position where the foliage dries quickly after rain. Nearly evergreen but may become untidy over winter. Very hardy andtolerant of neglect. Sizes vary considerably with the species. Propagate by cuttings, the species may also be grown from seed.
The 'Wormwood' family includes many aromatic species that were formerly used medicinally or for flavouring but which are now regarded as too poisonous for unrestricted use. Nevertheless they are attractive ornamental shrubs and perennials. Most have finely cut silvery grey foliage and small yellow flowers.
'Tarragon' (A. dracunculus) is still widely used as a culinary herb and has some medicinal uses too. The form 'Sativa', known as 'French Tarragon', is preferred for culinary use. It is an ingredient in many dressings and is also used to flavour vinegar.
Arthropodium (P) — G
The 'Renga Renga Lily' (A. cirrhatum) is a native perennial that is often mass planted as a quick filler. It forms a clump up to 1.5 m wide with bold strap-like leaves and small white flowers on 60 cm stems. These tough, adaptable plants are slightly frost tender and the new growth is liable to be attacked by slugs and snails. Plant in light shade with moist, humus rich soil. Propagate by seed or division.
Arum (P)
Many plants, especially Zantedeschia aethiopica, are commonly called arums, but A. italicum, a Mediterranean and Middle Eastern native, is the only true arum that is commonly seen. It has the sagittate (arrowhead-shaped) leaves that are so typical of aroid lilies. The foliage, which is deep green, often with cream veins, develops into a 25cm × 80cm clump. The flower, which appear in spring, has a translucent white papery spathe with a creamy yellow flower spike. The flower soon fades and is replaced by conspicuous bright orange red-berries in heads of 30 or so. It is easily grown in any moist soil in shade or partial shade and may become somewhat invasive. Some of the other species, such as the black arum' (A. palaestinum) are very striking, but they are only rarely available.
Aruncus (P)
Goat's beard is a very hardy perennial that tolerates wet soil and looks much like a giant Astilbe. It may reach 2 m × 1.5 m or more and is very impressive in full bloom although it is inclined to be untidy as it dies back. A. dioicus (sylvester) is the most common species. It has large sprays of very tiny creamy white flowers and fern-like foliage. Goat's beard may be grown from seed or divisions.
Arundo (P)
The giant reed, A. donax, is a very effective beside ponds or slow moving water courses. It is huge grassy plant that develops into a large clump about 2.5 m × 2.5 m. The variegated foliage form is more common than the green. Giant reed needs very moist soil and is capable of growing in at least 100mm of water. It prefers full sun or light shade and may be grown from seed or divisions.
Asperula (P) — R
Asperula gussonii has very small, somewhat silvery leaves and heads of tiny light pink flowers in spring. It forms a dense cushion about 6 cm × 20 cm wide and prefers moist well-drained soil in sun. Raise from seed, divisions or from small rooted pieces.
Astelia (P)
A native perennial genus often mistaken for flax (Phormium). Bold foliage plants for sun or light shade. Some also have attractive berry-like fruit in clusters. The best known form is A. 'Silver Spear', which has leaves of up to 1.2 m with metallic silver appearance. Astelias are easy, trouble free plants that should be more widely grown. Sizes vary considerably depending on the species. Propagate the species by seed and the hybrids by division.
Aster (P)
The Michaelmas daisies are primarily autumn flowering, while the alpine asters flower from late winter to mid spring. Michaelmas daisies and the novae angliae, A. × frickartii and A. × dumosus hybrids are rather prone to mildew in autumn and gardeners in humid northern areas may find this difficult to combat. The low-growing A. alpinus is not as susceptible to mildew. Asters range in size from ground covers through to plants that form 1.2 m × 1.2 m clumps. Plant asters in full sun and propagate by seed, division or cuttings. The annual asters are now classified under Callistephus.
Astilbe (P)
Astilbes create a soft graceful effect with their fern-like leaves and plumes of feathery flower heads. They come in many shades of red, pink, mauve and cream and in sizes from 30 cm - 1 m high. The common forms are hybrids of the Astilbe × arendsii and Astilbe × hybrida groups. Astilbes prefer in a moist position in sun or in shade. Division is the quickest means of propagation.
Astrantia (P)
While not always easy to find Astrantia is well worth the effort of locating. The papery flower bracts in shades of white, pink and green are very attractive and are good cut or dried flowers. Grow in a sunny or semi-shaded position that doesn't become too dry. The most common species is A. major, which grows to about 30 cm high x 40 cm wide. Very hardy. May be grown from seed or divisions of established clumps.
Aubrieta (P) — R
Aubrieta deltioides is a small spreading plants that covers itself in tiny pink, mauve, purple or white flowers in spring. It is best in full sun, but will tolerate partial shade. Aubrieta forms clumps about 15 cm x 50 cm. It is usually grown from seed but good forms can be perpetuated by division.
Aurinia (P) — R
The perennial Alyssum, of which A. saxatile is the best known species, are now known by this name. Hardy easily grown plants that are most at home in a sunny rockery. A. saxatile has masses of tiny yellow flowers in spring and early summer. The other species are similar. Propagate by seed. Sometimes grown from divisions or self layered pieces.
Azolla (A)
The common floating fern, A. rubra, can be found in nearly every area of still water. It is composed of bright green overlapping scales that turns deep red in the sun. It carpets the surface of the water and is useful as a quick cover to provide some shade, but it must be thinned regularly or it will completely cover the pond. Azolla requires nothing more than still water to grow and is usually self-propagating.
Babiana (B)
Several species of 'Baboon Flower' are grown, B. stricta is by far the most common. When not in flower the foliage clump could be mistaken for Freesia but for its covering of fine downy hairs. The small wide open trumpet flowers are borne in loose cluster on short stems held just above the 12 cm long leaves. The usual colour is purplish blue but white and yellow forms are occasionally available. Eventually makes a dense clump up to 30 cm in diameter. Of the other species B. rubrocyanea is distinctive because of the bright red centre to the blue flowers. Grow in light well drained soil in full sun. Propagate by seed or division of well established clumps.
Begonia (P)
Those most commonly grown begonias are the semperflorens, or bedding, forms, which are usually treated as annuals, and the × tuberhybrida, or tuberous, forms.
Bedding begonias come in wide range of colours and sizes, in both green and red-leafed forms. The new strains are sun tolerant but prefer moist soil conditions. Mildew can be a problem late in the season or in humid areas. Usually grown from seed, although fancy doubles may be propagated by cuttings.
The tuberous or × tuberhybrida begonias include a huge range of brilliantly coloured hybrids and are available in several growth forms. The smallest and hardiest are the multiflora forms commonly known as flamboyant begonias. These come in bright red, yellow and orange flowered forms and are popular for massed bedding. They bloom from late spring right through until the first frosts and are hardy enough to be left in the garden over winter in most coastal areas.
The larger multifloras and the bigger flowered are equally at home in the garden or in pots. They come in an enormous range of single colours as well as multi-coloured flowers, in both single and double forms. Trailing varieties for hanging baskets extend the range still further. Tuberous begonias have very fine, dust-like seed that can be tricky to raise; sow it at about 22°C. The tubers may be divided in spring, just as growth starts or you can strike sutting of the new spring shoots. All begonias are somewhat prone to mildew, especially in the autumn, although increasingly resistant strains are being developed.
Tuberous begonias generally grow best in moist humus rich soil in a warm but lightly shaded position. The flamboyants will tolerate full sun, provided they have good soil and are watered well.
Bellis (P)
Bellis perennis is a small daisy that is often treated as a winter and early spring
flowering annual. There are several bedding strains, which are available in
pink shades and white. They are undemanding plants, but rather prone to rust.
They are usually raised from seed, but fancy cultivars, such as 'Dresden China'
may be propagated by division or cuttings. Other species, particularly B.
rotundifolia, are occasionally sold by alpine specialists. Bellis daisies
are best in cool, moist soil in sun or light shade and may be short lived in
northern gardens.
Bergamot see Monarda
Bergenia (P)
The common B. cordifolia is a
widely grown for its bold foliage and the heads of bright pink flowers that
appear in early spring. It is very hardy and forms a 30 cm × 60 cm clump. Best
in cool moist shady positions. It is usually propagated by division.
Bleeding Heart see Dicentra
Borago (A) — H
In many areas borage (B. officianalis) is nothing more than a roadside weed. It is an annual with broad greyish green hairy leaves and heads of striking blue flowers that are covered in fine down. Herbalists use borage for medicinal purposes and as a flavouring. Grow in light well-drained soil in full sun. Raise from seed.
Brachycome (A & P)
The perennial B. multifida is a very popular low grower that is surprisingly hardy, it has masses of small pink, mauve or white daisy flowers from mid spring to early winter. The Swan River Daisy (B. iberidifolia) is similar, but annual. Both species form 15 cm × 25cm clumps. Plant Brachycome in a warm sunny position. Propagate by seed or cuttings. The native alpine species are sometimes available from specialists.
Brachyscome see Brachycome
Brodiaea (B)
These hardy North American corms are
easily grown in any sunny area with well drained soil. The foliage is
grass-like and fairly sparse. The dark purplish blue flowers are carried on
stems up to 45 cm high (in the case of B. elegans). Plants prefer to be
kept dry over summer and survive well on natural rainfall. This genus formerly
included many of the plants now listed under Dichelostemma and Triteleia.
Boltonia (P)
Very much like a tall michaelmas daisy, B.
asteroides has, in recent years, become a popular cut flower. The flower
stems, which may be up to 2 m high, bear hundreds of tiny daisies in white,
pink or mauve. Very easily grown in any sunny position. Propagate by seed,
division or cuttings.
Bulbinella (P)
A Southern Hemisphere genus that includes
a number of New Zealand natives. The grassy foliage is somewhat untidy but the
spikes of yellow flowers are attractive. Some of the larger South African
species, such as B. floribunda, are excellent cut flowers. Most species
have flower spikes about 75 cm high and develop into clumps about 50-80 cm
across. Grow in moist soil in full sun. Propagate by seed or division.
Calamintha (P) — H
Calamint (C. grandiflora) was once
an important medicinal herb but is now mainly grown as an ornamental although
some herbalists use it to make a tea, for which they use the whole plant.
Several species are grown , all of which as perennials with toothed ovate
leaves and spikes of pink or mauve flowers. Easily grown in any moist
well-drained soil in sun or light shade. Propagate by the division of
established clumps, basal cuttings or seed.
Calceolaria (P)
Calceolaria crenatiflora
has been extensively developed and is now a florists' speciality,
it is generally treated as an annual. It grows to 20cm × 25 cm and has pouch
shaped flowers in shades of red or yellow with contrasting markings. C.
integrifolia is larger and more shrubby in its growth habit and reliably
perennial. Both are best in cool moist shade. Propagate by seed or cuttings.
Calendula (A) — H
Calendula
forms 20 cm × 30 cm clumps of rather coarse foliage, but it is valued in mild
areas for its winter and early spring flower display. In cold winter regions
they are a summer annual. Many shades of cream through soft yellow to bright
orange are available. Calendula is easily grown in sun or light shade.
Although more familiar as an annual
bedding plant C. officianalis has been used as a medicinal herb and is
still used by herbalists to make a healing ointment for cuts. It is also used
to make an infusion to be taken internally and the golden flower petals can be
used for colouring.
Callistephus (A)
The annual asters are now classified
under this name. There are several strains of which the best known are the tall
(80 cm) 'Giant Crego' and the dwarf (40 cm) 'Comet' series. The daisy-like
flowers are large yet graceful. Available in shades of white, cream, pink,
mauve and red. The 'China Asters', which grow to about 80 cm are superb cut
flowers as well as being very attractive annual summer bedding plants. Asters
need a sunny well-drained position.
Calochortus (B)
The is a genus of some 60 species of
corms, mostly natives of California, commonly known as Mariposa tulips. The
foliage is grass-like to strappy. The species are divided into three divisions
based on the shape of their wiry-stemmed flowers. The Eucalochortus section has
pendulous flowers; the Mariposa section has wide open, upward facing blooms;
while those of the Cyclobothra section are cup-shaped and upward facing. Most
have flower stems between 20 cm and 45 cm high and develop into small clumps.
Mariposa tulips need ample moisture during the growing and flowering period
from spring to early summer but once flowering is finished they should be dried
off. The bulbs are only briefly dormant, they flower in spring, lose their
foliage around Christmas and come back into leaf in the autumn. Heavy frosts
may damage the winter foliage. A spot in full sun or very light shade with
light well-drained soil is best. Do not water after flowering. Propagate by
natural bulb offsets (some species form bulblets on their stems) or by
division.
Caltha (P)
Caltha palustris
is a hardy perennial bog plant with bright yellow buttercup flowers
and kidney-shaped deep green leaves. It develops into a 30 cm × 40 cm
clump. Double forms are available and there are also native species, such as
the tiny, white-flowered C. obtusa. They will grow in sun or shade and
may be propagated from seed, cuttings, or self rooted layers.
Camassia (P)
A genus of very hardy bulbous plants from
western North America. The most common species are C. cusickii, C.
leichtlinii and C. quamash. The grass-like foliage develops into a
dense clump but dies away quickly after the flowering season. The starry
flowers may be white, creamy yellow, pink or purplish blue depending on the
species. The are carried on stems up to 1.2 m high. The named forms of C.
quamash are the best of the blue shades and are often more compact plants.
Grow in sun or light shade in moist humus enriched soil. Requires ample summer
moisture. Propagate by seed or division of well established clumps.
Campanula (B & P) — G, R
A large genus that covers a wide range of
plants, all of which have the bell-shaped flowers that give the genus its name.
Bellflowers range from tiny rockery species, such as the 8 cm × 15 cm C.
cochlearifolia (pusilla) through to those, such as C. lactiflora,
that may reach 1.5 m or more. Canterbury bells (C. medium) is a biennial
species often used in cottage gardens and for general bedding. The ground cover
forms, especially the wonderfully named C. portenschlagiana and C. poscharskyana,
will rapidly cover an area up to 1.5 m × 1.5 m. They are also capable of
growing in the crevices in rock walls, some make good hanging basket specimens
too. The taller varieties with long stems are often excellent cut flowers.
Bellflowers generally prefer humus rich moist soil and a position in semi
shade. The perennials are usually propagated by division, cuttings or self
rooted layers.
Canna (P)
The bold foliage and flowers of the canna
lilies are a common garden feature. They are well known for vivid colours, but
are now also available in a wide range of pastel shades. Cannas can grow to 2 m
high, but dwarf forms that should not exceed 1 m are also available. Although
hardy enough to be grown over most of the country they do best in areas with
consistently warm summer conditions. Cannas prefer full sun and rich humus
filled soil. Propagate by division.
Cardiocrinum (B)
The 3–4 m high giant Himalayan lily (C.
giganteum) is one of the most impressive bulbs you can grow but it is not
for small gardens. It has large, leathery mid green leaves of the typical arum
lily arrowhead shape. The foliage develops very quickly in spring and the
flower heads of mature plants develop at a startling rate, so that by mid
December they are up to 4 m high. The cream and pink trumpet-shaped flowers,
which The resemble those of the regal lily (L. regale), are strongly
scented. The flowering clump dies after blooming, but is replaced by several
offsets that reach flowering size after 2–3 years. To ensure a continuation of
bloom, it is wise to have plants at various stages of growth. Raise a few from
seed (sow at 20°C), divide up your first flowering clumps, and once you have a
collection, leave a few to develop naturally. Cardiocrinum should be
grown in cool moist woodland conditions; semi shade and humus-enriched soil.
They are a perfect companion for rhododendrons and other shade-loving shrubs.
Carex (P)
This genus of grasses is very effective
at binding thin soils. Various foliage forms are available. All grow well and
quickly reach divisible size, which enables a good cover to be established.
Carthamnus (A & B) — H
Safflower (C. tinctorius) is an
annual to biennial species that is grown for its flowers, which are used to
produce food colouring and a dye. It is an untidy plant with stiff green stems
and slightly glossy lanceolate leaves. The bright golden yellow to orange
thistle-like flowers yield yellow or red dyes. The seeds are sometimes sold as
birdseed. Easily grown in any well-drained soil in full sun. Raise from seed.
Carum (B) — H
Caraway (C. carvi) seed has a very
pungent flavour and is often used in baking. It is a biennial with very finely
cut leaves and umbels of small white flowers. The young shoots can be used as a
vegetable or a pungent flavouring. Grows easily in any well-drained soil in
full sun. Raise from seed.
Catananche (P)
Cupid's dart is a very apt common name
for this hardy perennial. The pale blue tufted flowers resemble the flights of
a dart, and the long stem, the point. A very hardy perennial that is very much
like a cornflower in general habit. Easily grown in a sunny position, the
flower stems reach about 60 cm high. A soil on the dry side is preferred. There
are several similar forms of C. caerulea. Propagate by seed or division
of established clumps.
Celmisia (P)
One of the most attractive native genera
yet inclined to be tricky in cultivation. The foliage is usually a deep green
with a silvery grey reverse. The flowers are large white daisies with prominent
yellow stamens. Sizes range from minute alpines to large clump forming
perennials.
Many species simply refuse to grow
outside their native habitat but some are suitable for garden use. Of the C.
coriacea is probably the most adaptable. A genuine scree soil that is well
drained on top but cool and moisture retentive below is the key to success.
Generally unsuccessful in mild humid areas. Grow from seed.
Cerastium (P) — G
'Snow in Summer' is a silver leafed
perennial that smothers itself in small white flowers. Easily grown but
inclined to become untidy after a few years.
Celosia (A)
Cockscomb is a showy annual that needs
plenty of sun and warmth to produce good flowers. There are two main flower
types: plume and crested. Plume flowers are feather-like, while the crested is
a very unusual form in which the flower is twisted and recurved; both forms
grow to about 45 cm × 20 cm. The colours are typically bright gold,
orange and red but new strains are available in many shades. The foliage is
often is often a similar colour to the flower.
Centaurea (A & P)
The familiar annual blue cornflower (C.
cyanus) is but one of over 500 species in this genus, which also includes
some very impressive perennials. C. macrocephala is probably the best
known, but C. dealbata, C. argentea and C. montana are also
common. They cover a wide range of sizes from 20 cm to 1.5 m high. Flower
colours include blue, yellow, white, pink and reddish shades. Best in full sun
with excellent drainage. Propagate by seed or division.
Cheiranthus (B & P)
The wallflowers are useful for a splash
of colour when there isn't much else about. The biennial bedders will often
flower in winter in mild areas, while the perennials seem to flower year round.
They are very easily grown in any moist soil in sun or semi-shade. Propagate
the biennials from seed and the perennial from cuttings. Biennials rarely
exceed 40 cm × 30 cm, but perennials may reach 75 cm × 1 m.
Chionodoxa (B)
Glory of the snow (C. luciliae) is
a popular spring flowering bulb. In areas subject to winter snow they really
live up to their name but in most districts they tend to become lost among the
mass of spring bulbs. The foliage is grass-like and the small starry white eyed
blue flowers are carried in clusters of about 6-10 blooms on 15 cm stems. Very
hardy and easily grown in any well drained soil in sun or very light shade.
Other species, such as the pure blue C. sardensis, may occasionally be
seen. Propagate by seen or natural offsets.
Chlidanthus (B)
The sea daffodil (C. fragrans) is
not a daffodil but an amaryllid. The mildly fragrant bright yellow trumpet-like
flowers are carried in clusters of 3-5 blooms on 40 cm stems. Flowers in spring
and early summer and is an excellent cut bloom. Easily grown in any well
drained soil in full sun. Grows well in coastal conditions but adapts well to
most gardens. As with most amaryllids plant with the neck of the bulb at, or
just above, the surface. Propagate by seed, offsets or the division of well
established clumps.
Chrysanthemum (P)
The florists' chrysanthemums (C.
morifolium, C. indicum and their hybrids) are available in a bewildering
array of sizes, colours and flower forms. As with many large groups of hybrids,
chrysanthemums have been sub-divided into smaller groups based on flower type
and growth habit. Specialist growers list their plants by categories, such as
anemone, incurved, and fantasy.
Chrysanthemum extend the flowering season
more than probably any other tall perennial: they often flower until early
winter and can be forced into bloom out of season. However, getting the best
out of them demands some attention to detail. Chrysanthemums are often damaged
by chrysanthemum midge and powdery mildew. The midge larvae burrow into the
leaf and produce small raised lumps that can be very disfiguring. A systemic
insecticide is the only certain method of control. Regular pinching of the
lateral flowers is also necessary to secure the largest blooms.
Chrysanthemums strike easily from
cuttings; autumn is the preferred time. The young plants may need to be
wintered over under cover in cold areas and will need to pinched back in mid
spring and mid summer to produce strong stems and the best blooms.
Many of the plants formerly listed under Chrysanthemum
have been transferred to other genera and in fact the plants covered here no
longer belong in the genus. However, it will be some time before Dendranthema
becomes a widely used name.
Cichorium (P) — H
Chicory (C. intybus) is a
perennial that can be found growing wild in many areas. Its general appearance
is that of a light blue flowered dandelion. It has been used medicinally but it
is most commonly used as a vegetable and a flavouring. The long fleshy taproot
is the part most commonly used but the leaves and flowers are also edible.
Grows in any soil in sun or very light shade. Raise from seed.
Clarkia (A)
This genus of annuals now includes Godetia
although you will find plants sold under both names. The larger azalea flowered
forms of this genus are very useful for backgrounds or for mixing with other
tall annuals and perennials. The plants and seed sold for producing bedding
plants are mainly selections or hybrids of four species, C. amoena, C.
concinna, C. pulchella and C. unguiculata. Grown as cool season
annuals in mild areas and spring to summer annuals where winters are cold. Most
forms reach 50–75 cm high × 30 cm wide. Plant in moist soil in sun or
semi-shade. Propagate by seed.
Cleome (A)
The spidery pink and white flowers of Cleome
hassleriana (syn. C. spinosa) appeal as much for their
novelty as their beauty. It is tall (up to 1.5 m) and shrubby and very
effective as a background or centre-piece. Regular dead-heading is necessary to
ensure a succession of bloom. Cleome should be planted in full sun with
moist soil.
Clivia (B)
A genus of 4 species from South Africa.
The most popular species, C. miniata is common outdoors in near
frost-free areas but where temperatures regularly fall below -3°C it is a
greenhouse or conservatory plant. C. miniata has 60 cm long broad
strap-like leaves similar to Agapanthus and 20 or so bright yellow and
orange flowers clustered at the tip of each 50 cm stem. The flowering
season varies with the climate, but is predominantly autumn to mid spring. The
plants are largely dormant in summer, although they retain most of their
foliage, which is often damaged by slugs and snails. Clivia requires a
warm position with moist well-drained soil. C. nobilis is similar but
smaller with tubular flowers. It is better suited to cool climates but it is
still not very hardy.
Colchicum (B)
This is a widespread Eurasian genus of
some 70 species. While commonly known as autumn crocus, this genus is not all
that closely related to the spring-flowering crocus (Crocus). Colchicum
flowers in late summer and autumn and, apart from this most obvious
difference, Colchicum is in the lily family (Liliaceae) and has flowers
with six stamens, whereas Crocus is in the iris family (Iridaceae) and
has flowers with only three stamens. Autumn crocus flowers are usually white,
pink or mauve, but they vary in size and shape. Some are small and starry,
others large and cup-shaped and some have very fully double flowers like the
violet-pink C. speciosum 'Waterlily'. They are easily grown in any
moist, well-drained soil in sun or light shade. Colchicum seldom sets
seed but it is available commercially (stratify and sow at 18°C). Sternbergia
is a similar looking plant with yellow flowers. However, despite its similar
appearance it belongs to an entirely different family: the Amaryllidaceae.
Coleus (P)
The bold foliage colours of Coleus
have an instant appeal, they are perennial in warm areas, but are generally
treated as annuals. They are grown purely for the coloured foliage, the small
purple flowers are insignificant and should be removed immediately they appear
as they weaken the plant. Several strains are available with varying patterns
and leaf sizes. Some can become quite large but should be kept trimmed to
around 50 cm × 50 cm. Propagate from seed or cuttings, which strike extremely
easily.
Consolida (A)
Larkspur (Consolida ambigua) grows
to about 1.2 m × 30 cm and resembles a small delphinium. It is widely grown for
its bold and long lasting flowers, which are also excellent when cut or dried.
Larkspur is now available in many shades of white, blue, pink and red. It grows
best in full sun with moist soil and should be sown in situ or planted out when
very young as the roots resent disturbance.
Convallaria (P)
Lily of the valley (C. is famed
for its perfume but can become very invasive and hard to eliminate.
Nevertheless, there are far less attractive weeds. Grows in moist to wet soil
and becomes particularly lush if well fed. Prefers full shade but sun tolerant
if kept moist. The white, or occasionally pink, bell-shaped flowers appear in
early spring followed by bright orange toxic berries. Very hardy. Propagate by
seed or division.
Convolvulus (P) — G
Like Oxalis this is much
misunderstood genus; not all Convolvulus are rampant weeds. C.
sabatius (syn. C. mauritanica) has beautiful purple flowers and is a
restrained grower well suited to use as a rockery ground cover. The spreading
forms of the closely related genus Clytostoma are also attractive.
Coreopsis (A &P)
Coreopsis
can be relied upon to provide colour despite poor soil and neglect. The annual C.
tinctoria is available in shades of yellow, bronze and red, but the
perennials are all bright golden yellow. They are easily grown in light soil in
a sunny position. Some of the larger perennial species, such as C.
verticillata, may grow to 1 m tall but most are considerably smaller.
Propagate by seed or cuttings, large clumps can be divided.
Coriandrum (A) — H
Coriander (C. sativum) is an
annual with deep green pinnate leaves composed of rounded, broadly toothed
leaflets. The small white or mauve flowers appear in summer and are followed by
the seeds, which are the part of the plant that is used. Coriander seeds are a
common ingredient in spice mixtures and are also used on their own to provide a
distinctive flavour. The leaves and root can also be used but seldom are. Grow
in moist well-drained soil in full sun. Raise from seed.
Cosmos (A)
The bedding hybrids, such as the
'Seashell' mix are widely grown, they have lacy foliage and simple flowers.
Cosmos prefers a sunny position in light soil. The taller forms of grow to 1 m
high but most are around 50 cm x 50 cm. The perennial black or chocolate cosmos
(C. atrosanguineus) is also quite widely grown. It has very deep red
flowers, grows to 60 cm × 1 m and is propagated by cuttings or division.
Cotula (P) — R
Most gardeners will be familiar with this
genus of perennial daisies through its use as a surface for bowling greens. The
rockery species are all very compact clump forming or slightly spreading
plants. The most attractive species is the native C. atrata, which has
fine ferny foliage and deep blackish-red flowers in summer. It grows to about
10 cm × 30 cm and is a natural scree plant that will grow in sun or
very light shade. Propagate by seed, cuttings, natural layers or division.
Crinum (B)
Closely related to Amaryllis these
large clump forming bulbs have a reputation of being somewhat tender but they
can be successfully cultivated outdoors over much of the country with a little
protection. The most widely grown is C. x powellii and related hybrids
but you may also see C. moorei. The long strap-like leaves may grow to 1
m long and the flower stems are up to 1.5 m high. Each stem carries several 100
mm diameter trumpet shaped flowers that are often very fragrant. Plant in sun
or very light shade in moist, well drained, humus enriched soil. Crinum
needs ample moisture and feeding when in active growth. Propagate by seed or
division of established clumps. The bulbs are huge (weighing about 1.5kg) and
clumps can be difficult to break up.
Crocosmia (B)
The best known of this late summer and
autumn-flowering South African genus of Gladiolus relatives is the
bright orange flowered montbretia (C. × crocosmiiflora). However, this
hybrid between C. potsii and C. aurea is virtually a roadside
weed in many areas and is now seldom cultivated in gardens. The more widely
grown garden specimens are C. masonorum and C. paniculata, which
have strappy, deeply ribbed foliage similar to montbretia, but with larger and
longer flower stems (around 75 cm for C. masonorum and up to 1.2 m for C.
paniculata). They come in a range of yellowish-orange and to rusty red
shades and well-established clumps with stems arching in all directions are
very attractive. Crocosmia does best in sun or light shade in
moist, well-drained soil, although they will tolerate considerable drought.
Crocus (B) — H
One of the most widely grown and recognised of the spring bulbs. The earliest crocuses are often in flower by mid winter but the bulk of the bloom comes from early August to mid September. In all species the foliage is more or less grass-like and the flowers vary little from the standard goblet shape. However, the range of colour and pattern is vast. The best known species is C. vernus but specialist growers list many species and hybrids.
Saffron (C. sativus) is the most
expensive herbal product. It is made from the bright orange stigmas of a Middle
Eastern crocus. The vast numbers of plants required and the labour involved
account for this colouring and flavouring's high price. It is possible to grow
your own, the species requires no more care than any other crocus.
Crocuses are often naturalised in lawns
and this is one of the most effective ways to grow them although you must, of
course, be careful about mowing times. For general garden use plant in sun or
light shade in moist well drained soil. In wet mild winter areas with humid
summers crocuses can be difficult but in general they pose few problems.
Propagate by seed, if available, otherwise by natural offsets or the division
of established clumps.
Cuminum (A) — H
Cumin (C. cyminum) is an annual with finely cut leaves and heads of small white or pale pink flowers that resemble yarrow umbels. Although once regarded as a medicinal herb the seeds are now used primarily for culinary purposes and are one of the main ingredients of curry. Grow in moist well-drained soil in position sheltered from cold draughts. Raise from seed.
Cyclamen (P)
A wdiespread Eurasian genus of about 15
species. Understanding the species is complicated by the many name changes that
have occured over they years. For example, the plant currently known as C.
vernum has been previously classified as C. orbiculatum, C. ibericum, C.
hiemale and C. atkinsii. The florists' cyclamen (C. persicum)
can be grown outdoors in mild areas but more rewarding in the long term are the
smaller, less flamboyant species often known as rock cyclamen. The best known
of these is the autumn-flowering C. hederifolium (neapolitanum)
but specialist growers can supply many other species, including C. repandum,
which is similar to C. persicum but easier to grow. These smaller
species develop into neat little clumps that are perfect for shaded rockeries
or woodland areas; some flower in autumn, others in spring. Plant in
well-drained, humus-enriched soil that never lies wet. May be grown in sun in
cool areas otherwise light shade is best. Cyclamen should be planted
with the tuber protruding about halfway above the soil surface. Propagate by
seed (sow at about 16°C) as the tubers multiply very slowly.
Cyperus (P)
Some of the Cyperus sedges, such
as nut grass (C. rotundus), are extremely serious weeds. However, the
ornamental species, such as papyrus (C. papyrus) and umbrella plant (C.
alternifolius), are very useful marginal plants. They have strongly upright
grassy stems and very prominent greenish-brown flower and seed heads on
thickened stalks up to 1.5 m high or more. They will grow in up to
50 mm of water but require warm summer conditions to do well. Propagate by
seed or division.
Dahlia (P)
There are only a dozen or so dahlia species
but countless cultivars. The cultivars are divided into groups based on flower
and growth characteristics. Specialist growers or books will provide details of
these groups. Dahlias are available in a wide range of sizes. The smallest are
the miniature cultivars, which grow to about 30 cm x 30 cm. Next are the
bedding dahlias, which are usually treated as annuals, they grow to about 60 cm
x 50 cm. The larger hybrids may exceed 1.5 m, while the tree dahlia (D.
imperialis) can grow to 4 m or more. It has soft pink flowers and blooms in
the autumn.
The large tubers are best lifted in cold
areas. Even in mild areas they should be lifted and divided every two or three
years or the flower quality and quantity may suffer. Store the tubers in sand
or sawdust in a frost-free, dark place. They may be divided before replanting.
Cuttings of the new spring growth strike quickly.
Dahlias are best planted in full sun or
partial shade in a rich humus filled soil. Pinching back and disbudding is
necessary if show blooms are required. Dahlias are subject to caterpillar and
thrips infestation and powdery mildew, which almost always develops in autumn,
but as the plants are nearing dormancy control is not always necessary.
Delphinium (P)
Dephiniums are the ideal perennial —
brilliant colours, quick growth, easy-care, and a very distinctive spire-like
growth habit. Look at any good perennial border and you will see delphiniums;
they are absolutely indispensable.
The most widely grown delphiniums are the
Pacific Giant hybrids, which grow up to 2 m high and cover a range of white,
pink, mauve and blue shades. The 'Magic Fountains' are around 1.2 m high with a
similar colours. Many other hybrid selections are grown in Europe but seldom
seen here. A collection of Delphinium species, which are often very
different from the hybrids, makes an interesting display.
Grow in full sun in rich but free
draining soil. Mildew can be a problem in autumn and although the plants are
nearing dormancy at this time the problem should be treated, as delphiniums are
not fully deciduous and the disease may be carried over to following season if
left untreated.
Dianthus (B & P)
This genus includes the perennial border
pinks and the carnations. as well as the biennial bedding plants and sweet
William, which are both usually treated as annuals. They are often valued as
much for their fragrance as the beauty of their flowers.
The many species and hybrid forms vary
considerably. The tiny cushion pinks, which are so charming in rockeries, are
no more that a few centimetres high, even when in flower. The florists'
carnations, however, have flower stems up to 60 cm long (they often need
staking) and in-between are the border pinks and the bedding dianthus, which
grow into 20 cm × 30 cm mounds.
They are primarily spring- and early
summer-flowering although the fancy hybrid carnations are often forced into
bloom out of season. All dianthus grow best grown in full sun and light or
gritty soil and the larger carnations require regular feeding with dilute
liquid fertiliser to keep them flowering well. Propagate the bedding varieties
from seed, the perennials and hybrids from small cuttings (slips).
Diascia (A & P)
The two spurs found on the bright pink
flowers of this southern African genus account for the name 'Twinflower' or
'Twinspur'. They are easily grown in any sunny position. The smaller perennial
species are superb rockery plants that flower heavily over a long season and
appear to be reliably hardy in all but the coldest or wettest areas. Propagate
by seed or cuttings.
Dicentra (P)
Most gardeners are familiar with the
common pink 'Bleeding Heart' (D. spectabilis) but there are many other
species and hybrids. At 1 m × 1 m, D. spectabilis, is the largest
growing under our conditions, others, such as D. eximea, D. cucullaria
and D. formosa, are smaller. All are available with pink or white
flowers. They are best grown in moist humus rich soils in light shade, although
most are sun tolerant provided they are kept moist. Some of the forms of D.
formosa, particularly 'Bountiful' can become slightly invasive. Propagate
by seed, cuttings or division.
Dichondra (P) — G
Mercury Bay Weed is a widely planted lawn
substitute. Not hardy in cold areas it also needs ample water to be at its
best.
Dierama (B)
Lady's wand, D. pulcherrimum, is
the best known species. The foliage is similar to that of Watsonia but
the flower stems are very distinctive. They grow up to 2 m high and gracefully
arch under the weight of the pendulous bell-shaped flowers they carry along
their length. The flowering season is early to mid summer with a few later
blooms. Colours range from very pale pink to purple. The smaller, slightly
earlier flowering, D. pendulum may occasionally be seen. Easily grown in
any well drained moist soil in sun. Propagate by seed, which sometimes
self-sows, natural offsets or the division of well established clumps.
Dietes (B)
This genus includes several species
formerly listed under Moraea. The most common species is D. bicolor
(Moraea bicolor). This plant, including the flowers, is very iris-like
in appearance. The small to medium sized blooms are a pale creamy yellow with
conspicuous maroon markings. The flowers may appear at any time but tend to
come in bursts every two weeks through the warmer seasons hence the name 'Fortnight
Lily'. Easily grown in any moist, humus enriched soil in sun or light shade.
Very effective near ponds. Propagate by seed or the division of well
established clumps.
Digitalis (B & P)
Foxgloves add height to a border and
despite their height they seldom need staking. Digitalis purpurea, the
common biennial foxglove, will grow almost anywhere but is best in a moist,
humus enriched, soil. It is sun tolerant if kept moist, otherwise very light
shade is better. Most forms will grow to 1.5 m x 75 cm or more, but the 'Foxy'
series is a dwarf seedling strain that grows to about 1 m. Propagate by seed,
basal cuttings or division.
Dipsacus (P) — H
Teasel (D. fullonum) and Fullers
teasel (D. sativus) are nowadays primarily grown as ornamentals and for
their seed heads, which are used as dried decorations. It was used as a
medicinal herb in the middle ages and the spiny seed heads have long been used
for combing wool. These species are hardy biennials with strong upright stems
that grow to about 2 m high. They have lanceolate leaves and small lavender
flowers in rounded heads. These heads develop into the characteristic seed
heads. Grow in moist well-drained soil in sun. Raise from seed.
Doronicum (B)
'Leopard's Bane' is a fairly coarse
perennial that is best suited to large perennial borders. It is not really
attractive enough to be a specimen plant and is too large and sprawling for
small gardens. Several species and forms are available, all bear bright yellow
daisy flowers on long stems. The heart shaped leaves are dark green. Grows best
in woodland conditions. Moist, humus enriched, well drained soil in light
shade.
Dorotheanthus (A)
Commonly known as 'Livingstone Daisy'
these annual succulents always give a vivid display in hot dry positions. New
strains come in a wide range of colours, the only shades missing seem to be
blue and purple. They develop into 15 cm × 20 cm clumps and must be grown in
full sun.
Echinacea (P) — H
Cone flowers are unusual plants, they are
stiffly erect with pink or white daisy flowers on stems that can grow to 1.5 m
or more. The petals of the common species, E. purpurea, hang down, which
gives it a very distinctive appearance.
Coneflower (E. purpurea) is most
commonly seen as a garden ornamental but it is also used to make a herbal
tonic. A similar species (E. angustifolia) is supposedly more effective
than the common perennial. Both species have deep green ovate leaves and
stiffly erect pinkish purple daisy flowers.
The seed heads may be used in dried
arrangements. Cone flowers should be planted in full sun with light,
well-drained soil. Propagate by seed or division.
