The spring garden
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How was your spring garden this year? Did you have plenty of colour and variety right from the first snowdrop through to the last rhododendron? Did you have sun in the right places and shade where you needed it?
If you can answer yes to these questions you can be fairly satisfied. If not, it’s time to start planning and making change with next spring in mind. The first spring bulbs are delivered to the shops in midsummer so you need to start making planting plans well in advance.
While shrubs, and to a large extent perennials, can be planted at any time throughout the year, bulbs require more forethought and planning. Drifts of crocuses and daffodils may seem to appear almost from nowhere but in reality they don’t happen overnight.
Planning for spring bulbs depends greatly on how you intend to use them. Without doubt they are most effective when massed rather than used for spot colour, but would you prefer beds of bulbs, pots or the natural look: growing in grass or in a rockery?
Bulbs in garden beds
Beds of massed bulbs are probably the quickest way of ensuring a bright display. Site your beds where they will receive at least half-day sun and where they will be free-draining. Work over the soil well in advance of planting, add a little bonemeal or bulb fertiliser and rake the surface to a fine tilth. The soil needs to fine, preferably slightly sandy, so that the soft growing tips of the bulbs are not impeded as they push up through the soil. This is especially true for tulips, the soft foliage of which is easily damaged, but not so important for toughies like daffodils and snowflakes.
When choosing a selection of bulbs you need to consider their flowering times and how they will look after blooming. This will greatly influence the layout of your beds. For example, most daffodils flower before the tulips have fully developed foliage. Daffodils can be quite unsightly after flowering and old, browning daffodil foliage lying all over your tulips may not be the effect you had envisaged.
If you want to mix genera, you would be better to combine hyacinths with the daffodils rather than tulips as they flower at much the same time. Better still, stick with one genus but mix species and cultivars for variety.
While beds of bulbs alone undoubtedly create spectacular colour in season, they can look very bare after the flowering. Consider combining bulbs with perennials or small shrubs to keep things looking green.
There are pitfalls to be wary of in combinations. You don’t want to have large patches of dry and dying bulb foliage among your perennials just at the time when the perennials should be looking their best. The ideal combination is to have the bulbs edge the perennials, which will then develop to hide the foliage of the bulbs as it dies back. Daffodils and daylilies for example, combine well as the daylily foliage will merge with and hide the daffodil foliage as it dies off. Hostas and tulips are equally compatible provided the tulips get enough sun to flower well.
When combining bulbs with perennials it is best to keep the bulbs at the back of the bed so the developing perennial foliage hides the fading bulb foliage. With shrubs the emphasis shifts to ensuring that the bulbs receive enough sunlight to develop properly.
Having decided what to plant and how to arrange the bulbs, we come to that ever-recurring question: how deep do you plant bulbs? Well, there’s no absolute rule for planting depth. Most authorities recommend planting to depth rough equivalent to twice the length or height of the bulb, or slightly deeper in sandy soils. While obviously incorrect for the likes of belladonna lilies and nerines, this rule generally holds true for spring-flowering bulbs. Also, in order to give the roots room to develop, prepare the soil to about 10 cm below the planting depth. Fortunately, provided you don’t get it completely wrong, most bulbs will find their own level in the soil after a few years.
Another common question is which way is up? Usually that’s fairly obvious — the remnants of the roots will be visible — but sometimes it can be hard to tell. Most bulbs are longer than they are wide so at least you can pick the top and bottom from the sides even if it's hard to tell bottom from top. This means that if in doubt you can always lay the bulbs on their sides and leave nature to sort out the problem.
Bulbs in pots
There’s nothing very tricky about growing bulbs in pots. Just remember to incorporate some coarse drainage material in the base of the pot and use a good free-draining potting mix.
Plant at the same depth as you would in the garden and ensure that the pot is deep enough to ensure good root development.
Do not plant bulbs in pots while the weather is hot. If exposed to excessive heat, as may be experienced in a pot in a hot, sunny position, many spring bulbs will start to split up and deteriorate. Tulips and Dutch irises are particularly prone to this. It is better to keep the bulbs somewhere cool and dry, say in a garage or garden shed, until the weather starts to cool off in autumn. Don’t leave planting much beyond the end of March, however, or the roots may not develop properly.
Naturalising bulbs in grass or rockeries
Once established, naturalised bulbs generally take care of themselves. All that is required after the initial planting is an occasional feeding and a little extra care when mowing or weeding.
Most small bulbs will naturalise quite freely in well drained rockeries with a decent depth of soil. Dwarf daffodils, irises, lachenalias, fritillaries and glory of the snow (Chionodoxa) are ideal candidates. Plant as you would in pots or beds and mulch the surface with a layer of fine shingle chips to keep the bulbs cool and make weeding a bit easier.
Naturalising in lawns or fields requires a bit more planning. You need to be especially careful when siting the bulbs. Avoid places where rainfall runoff is likely to collect, consider how the development of trees and shrubs is likely to affect future shading, think about garden access (it’s no good having bulbs where you have to walk frequently), and make sure that the bulbs are in a place where it’s not important that the grass is short.
Thoroughly prepare the soil, paying particular attention to drainage. The idea is that you won’t be digging over this area for years, but with poorly drained or easily compacted soil your plans may come unstuck. A large rotary hoe will work the soil to a decent depth and a fine tilth. It is also an ideal tool for thoroughly incorporating fertiliser. Failing a rotary hoe you’ll have to resort to the fork and rake.
Plant as for garden beds and then oversow with grass. Where possible choose a fairly short grass, such as a variety of fescue, that won’t overwhelm the bulbs or require too much mowing.
The bulbs will flower in the first year but the grass may become rank, tempting you to mow too early. Don’t attempt to mow the grass while the bulb foliage is still green. Leave it to die off naturally because, like any other plants, bulbs depend on their foliage for photosynthesis. The foliage doesn’t need to be completely dried before mowing, but there should be no more than a couple of centimetres of green stem remaining.
When you will be able to mow depends on the bulb selection. Early flowering bulbs, such as crocuses, snowdrops and daffodils, generally dry off quickly after flowering, which will allow mowing by early to mid December in most areas, bluebells may take longer.
Perennials
Perennials are among the simplest plants to cultivate yet are also capable of causing plenty of difficulties for beginners who are unfamiliar with their growth habits. Perennials look so innocent sitting dormant in those little pots at the nursery. It’s hard to imagine that they could grow so rampantly or so large. Yet anyone who has planted a gunnera or large rudbeckia in the wrong place soon learns from their mistakes. Fortunately, most perennials are easily transplanted when dormant and can be tamed.
Few perennial make much of a show in the spring garden. They tend to flower most heavily in early to mid summer. Nevertheless, you need to be aware of how quickly their foliage can develop.
Some, like the bergenias, buttercups pulmonarias, and small primroses are spring flowering. And of course the ice plants, gazanias, arctotis and all those other perennial daisies are indispensable for spring colour in hot, dry corners. However, these are plants that don’t require much planning unless they are to dominate the garden. In most cases it’s just a matter of dotting them around and shifting them about until you get the right effect.
Shrubs and trees
Bulbs may be the things that first grab our attention in early spring but by mid September our thoughts are turning to the larger plants, the trees and shrubs. Cherries, almonds, crab-apples, magnolias, azaleas and rhododendrons are spectacular plants that provide interest well beyond spring and which often act as the framework of a garden.
Planning is largely a matter of deciding on plant size, foliage type and colour, flower colour and blooming season. It’s often better to choose the easily transplanted specimens like the azaleas and rhododendrons in bloom so you can be sure of the colour. The deciduous trees are shrubs are usually more readily available and better planted in winter when they are dormant.
While you may not be planting for some time it is nevertheless wise to start planning early while you still have an appreciation of how these larger plants will affect the rest of the garden. It’s all too easy to plant a large deciduous tree in winter with little thought to where it will cast its shade, only to find that it needs to be moved come summer.
Now, during summer, work out where shade and shelter will be of most benefit as well as determining which areas are best left more open and exposed. If a decent selection of specimens is available during the growing season, there’s nothing to stop you planting right away. Do remember, though, to water the plants well if you plant in summer.
Thinning or moving trees to let in more light or provide shade
Despite your best efforts trees may have been planted in the wrong places or have grown too large. Excess shading can lead to cold, damp, dark corners where few plants will grow. Most of the spring-flowering trees can be pruned in summer, indeed Prunus species (cherries, apricots, almonds, etc.) should be summer-pruned to avoid silverleaf disease. Now is a good time to do a little judicious thinning of the ornamental varieties to let in more light and air.
Gardeners who become nervous wrecks at the thought of pruning in winter, when they can’t see how the plant will develop, tend to go overboard in summer because they can see instant results. Take it slowly and carefully and aim to simply open up the structure of the tree rather than hacking it back severely.
Consider moving any shrubs or trees that are in completely the wrong places. While not all are suitable for transplanting most deciduous trees can be safely moved when dormant. If prepared well in advance of the shift, many evergreens are transplantable too.
Garden centre staff or an arborist can advise you about the timing, the best methods and little tips for particular species. Usually the technique is to “wrench” the tree well before moving. This involves digging a trench around the tree and loosening the roots well before moving. This reduces the root ball to more easily handled dimensions and encourages the tree to form new feeding roots within the smaller root ball. While you may prefer to err on the generous size with the root ball, remember that you have to be able to cut under the root ball and shift the plant. It is better to be more severe in your trenching early on and give the plant longer to recover before moving than to find that more roots need to be removed at shifting time.
The actual lifting can be very tricky and dangerous. Don’t underestimate how heavy a large shrub or small tree can be. Get several helpers and if at all possible use machinery rather than your back. If you can’t lift the plant to its new destination, consider using rollers or dragging it on a large tarpaulin.
Nurseries that specialise in large trees will be happy to do the hard work for you. If you are willing to part with otherwise excellent specimens that are simply too large or in the wrong place, they’ll even pay you for the privilege.
Choose a wide range of plants for variety
Whatever style of spring garden you prefer, make sure that you choose a wide enough selection of plants to ensure variety over a long season. Regular trips to your nursery or garden centre will give you an appreciation of what flowers when in your area. Generally the first plants to bloom are the camellias and the so-called winter-flowering shrubs (witch hazel, wintersweet and the like), next we see the early bulbs and cherries, then the magnolias and finally the azaleas and rhododendrons before the first roses signal the arrival of early summer.
These are the plants that mean spring to most of us, but they are all imports and of course we should not overlook our native New Zealand flora. While the kowhais are the best known of the spring-flowering natives, kaka beak (Clianthus puniceus), tainui (Pomaderris kumeraho), manuka, many olearias and the more easily cultivated of the Celmisia daisies also make a very colourful display.
Start working on the changes now and by next spring you should be approaching your ideal.
Copyright Geoff Bryant
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