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Trees

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Trees are a vital part of garden design, they provide height, shade, a buffer that lessens wind and noise, a playground for children and a home for garden wildlife. But just importantly, at least as far as gardeners are concerned, trees define a garden because they set the tone for all other plantings. Just as the nature of a European woodland is determined by the light shade and leaf-mould provided by a canopy of deciduous trees, and the New Zealand rainforest by its dense cover of lush evergreen foliage, so the style of your garden will be markedly influenced by the choice of trees.

Trees are large, most grow to at least 5 m × 3 m, but the dividing line between trees and shrubs is not always clear cut; for example, when does a magnolia become a tree rather than a large shrub? The traditional definition is that a tree is a large perennial plant with a single woody trunk and a crown of foliage, but don’t let that limit the way you use trees and large shrubs. Large shrubs can be trimmed to a single trunk and trained into a tree-like form if that suits your design and trees can be trained into multi-trunked forms for hedging or as a windbreak. As always, the only real limitation is your imagination.

Trees may be evergreen or deciduous, broadleaved or coniferous, they may be tall and narrow like a poplar or as squat and wide as a crab-apple. They may race up to 10m high within a few years or take many years to get to 2 m high. There are trees with all manner of foliage types and colours and there are also the more unusual forms, such as palms and tree-ferns, but ultimately size is the most important consideration when deciding which trees to plant. Most gardens need at least one tree, but as city gardens become smaller it is increasingly difficult to find trees that are suitable. If you live on a multi-hectare block in the country your selection of suitable trees is enormous, but move to a 50m² garden in the city and it dwindles to but a few. However, the difficulty is not the limited choice, rather the failure to acknowledge the limitation. So many people with small gardens insist on planting trees that will rapidly outgrow the site and cast the whole garden in deep shade. How often do you see trees that have outgrown the space allocated to them or that have been heavily pruned to make them fit? Don’t attempt to grow a tree unless you know that you can cope with it size.

Choosing your trees

Despite their importance, trees are often an afterthought in home gardens, the lawn is sown, the favourite shrubs and perennials are planted then the trees are positioned to provide shade or to block undesirable views. This is absolutely the wrong way to plant, the trees should be planted first, if for no other reason than that they can be expected to live for at least twenty years, which is far beyond the life of most other garden plants.

Practical considerations

Trees are generally permanent and, more than any other non-edible garden plants, they are usually required to perform functions other than being purely ornamental, so take time to choose the right trees and make sure that you base your choices on the right criteria. Before visiting a nursery you should know what size trees you want (spread as well as height) and what functions they are to perform. Wide-spreading trees cast more shade than narrow, upright trees, which are better suited to use as windbreaks or privacy screens. Deciduous trees are just as effective at providing summer shade, but they let in light in winter, while evergreens provide a better year round windbreak.

Equally importantly, any plant you choose must be able to survive in your climate and soil. Frost and wind tolerance and rainfall are the main climatic concerns, while drainage, depth, humus content, and pH are the most important soil considerations. The climate will also determine the rate of growth. Some trees are naturally fast growers but the more suitable the climate the quicker the tree will grow.

Where you intend to plant plays a vital part in tree selection. When siting trees bear in mind the layout of household drains and sewers. Removing tree roots from a blocked sewer is not one of life’s most pleasant jobs, and it’s not just a matter of cleaning out the plumbing, it usually also means removing the tree. You can save a lot of work and heartache by keeping trees away from pipework thereby minimising the risk.

The aspect and the angle of the sun, which varies with the season, determine how much shade a tree will cast. Any large tree will provide a considerable amount of shade throughout the year, but when the sun is at its lowest in winter, a wide-spreading tree can shade an entire city garden. Dense, heavily foliaged trees provide the best privacy but have little else in their favour; they cast too much shade, are less effective as wind breaks than more permeable trees and it’s very difficult to grow other plants under them. The ideal shade tree is deciduous and has a wide canopy of lacy open foliage, it protects from the heat of the midday summer sun but allows the breeze and the low-angled sunlight of morning and evening to penetrate. The silk tree (Albizia julibrissin) and the various forms of Gleditsia are excellent shade trees for small gardens.

Ornamental considerations

Given the choice, most gardeners will opt for evergreens over deciduous plants, the advantage of year round foliage is nearly always decisive. However, deciduous trees have plenty to offer, not just in terms of their superiority as shade and compost providers, but as ornamental plants too. Think of deciduous trees and the first thing that comes to mind is autumn foliage, those vivid tones of yellow, orange and red, but the bright green of the new spring growth should not be underestimated. There is also a wide range of summer foliage colour among the deciduous trees, the bright yellow of Robinia ‘Frisia’, the deep blackish red of the copper beeches (Fagus) and the silvery grey of the weeping silver pear (Pyrus salicifolia).

Conifers are generally thought of as being evergreen trees with needle-like foliage, but a few, such as the larch (Larix) are deciduous. Most develop into large trees but there are a few very dwarf species and others that don’t really match out usual ideas of conifer-like appearance. The best known of the ‘non conifer-like’ conifers is the ‘Ginkgo’, which is so distinctive that it is placed in a separate family and order by itself. It has broad leaf-like cladodophylls that in no way resemble needles and to all intents and purposes it looks like a broadleaved tree. Other conifers of unusual appearance include our native ‘Celery Pines’, which also have broad cladophylls.

The bark of a tree can also be very attractive. The paper bark maple (Acer griseum), silver birch (Betula pendula) have very distinctive bark, but few trees can match the eucalypts. This large Australian family shows an enormous variation in bark texture, colour and the degree to which it peels. Some species shed their bark entirely to reveal stark white trunks, others shed flakes of bark to create a multi-coloured effect, and some retain their bark, which may become a deep reddish brown. However, unlike fallen leaves, which all gardeners know makes the best compost, large pieces of bark take a long time to break down and can become a fire hazard.

All broadleaved trees flower, although not all are particularly colourful. The flowering cherries (Prunus), dogwoods (Cornus) and the large magnolias are often planted for their flowers but as far as most other temperate climate trees are concerned, flowers are often a secondary consideration. Tropical and sub-tropical trees are different, many have very spectacular flowers. The large Proteaceae family plants, such as the Queensland firewheel tree (Stenocarpus), the tree banksias and the larger grevillea are extremely colourful, but few can match the brilliant crimson blooms of our own pohutukawa (Metrosideros excelsa). Among the hardier trees the acacias and Judas tree (Cercis siliquastrum) are very colourful and distinctive.

Foliage colour, bark texture and flowers all contribute to the beauty of a tree, but size and form are generally more important. Don’t allow the beauty of a tree to cloud you judgement when it comes to choice because even the most beautiful tree can become a liability if it becomes too large.

Planting

Having chosen a suitable site and tree you must ensure that whatever you plant thrives. There’s a hackneyed old saying that says you shouldn’t plant a five dollar tree in a one dollar hole. Apart from the need to update it to take account of inflation, that old saying is perfectly true. As with just about every aspect of gardening the more time you put into preparation the better the results. When you’ve taken great care to plant the right tree in the right place, why rush to plant it?

The roots of a tree spread far more widely and deeply that those of a shrub. It’s not possible to incorporate enough compost and fertiliser to keep a tree happy for its entire life, so the best you can do is give it a good start. Dig over the soil to about 300 mm below the depth of the new tree’s root ball and to at least 500 mm greater diameter that its current root spread. That will allow the tree to establish new roots quickly, which will help to boost its growth and to stabilise it. Dig in plenty of fine compost to improve the soil texture and increase its moisture retention. If you live in an area with a hard clay sub-soil use a crowbar or a pick to break up the clay or you may find that your trees start to suffer from poor drainage and impeded root development once their roots strike the subsoil.

Remove the tree from its container and plant to the same depth as it was in the container. If the surface roots are showing you may plant a little deeper but take care that you don’t bury the union point of grafted or budded trees. Hammer in a stout stake before finally firming the tree into place, taking care not to damage the roots. The ground around the tree will need to be trodden down somewhat to firm up the tree, but don’t overdo it; it’s better to firmly stake the tree and keep the soil loose than it is to compact down all that soil you laboriously loosened up. In very dry areas or where the tree must fend for itself it's often a good idea to make a small ridge of soil around the drip-line of the tree. This ensures that any moisture dripping from the foliage is channelled back to the roots.

Having planted the tree you may feel the need to add fertiliser, but its usually best to let the tree establish first. If you apply fertiliser before the tree begins to grow it may develop a too compact root system because there is no need for new roots to form and seek out soil nutrients. Making the tree stable should be your first consideration, staking helps but encouraging a quick root spread is the best way. When you apply fertiliser put it just outside the drip-line and water it in well to encourage the roots to spread downwards and outwards.

Modern nursery practice dictates that most plants are now grown in containers, but large deciduous trees are the exception — the majority are still lifted from the open ground. This is usually done in winter when the trees are dormant. Ideally the nursery will pot the trees after lifting, but if you buy a bare rooted deciduous tree it must be planted right away. Once established in large container, trees lifted from the open ground may be treated just like container grown plants. They may be planted at any time, provided the soil is in a suitable condition to work and the weather is not exceptionally hot or cold.

Of course you don’t have to plant out, trees can be grown in containers permanently. However, a large tree in a large pot is very heavy and unwieldy, and will have considerable watering and feeding demands. Generally potted trees are treated as temporary plants that are transplanted to the garden when they become too large to be comfortably repotted.

Maintenance

Maintenance is most important during the first two years after final planting, established trees can largely look after themselves. Trimming to shape, loosening ties and restaking, fertilising and watering are all necessary to ensure that your trees get the best start.

Unless you intend to train a tree to a specific shape or style of growth, the pruning of young trees is generally just a matter of removing any damaged branches and those that are likely to head off at strange angles. Garden trees often look better if they’re allowed to develop naturally, just aim to maintain a clean trunk with good canopy development, there’s no need to prune to a perfectly straight trunked forestry specimen.

If they have been planted in the right place established trees rarely need pruning unless they have been damaged in some way. If a large tree has to be trimmed, it’s a job best left to professional tree surgeons. Very few gardeners have the necessary ladders and climbing equipment to scale a large tree, let alone the experience to safely trim the tree once up it. Likewise, felling a tree, especially in a built-up area demands experience.

A young, newly planted tree with a large head of foliage is very likely to be damaged by the wind, either by directly damaging the superstructure or by causing the tree to rock, which may weaken the tree at ground level or damage the roots. Young trees must be firmly staked, but staking can cause problems too. Young trees have soft bark that is easily damaged if it continually rubs against a stake or against the ties that hold the tree to the stake. As the tree grows, its trunk and branches increase in diameter, which can cause the stake and ties to cut into the bark. Use ties made of a soft material that breaks down with time and regularly check that the ties are still slightly loose and the stake is not cutting into the trunk. The new foam rubber tree ties are excellent and can be adjusted as the tree grows, but strips of old cloth are really just as good and they are biodegradable. In most cases the stake can be removed after two years, often sooner, but don’t underestimate the strength of the wind.

Young trees will establish more quickly if fed and watered, but as mentioned earlier this is better kept at a subsistence level in order to encourage good root development. Established trees will also benefit from feeding, especially if their roots are at all confined. Use a general garden fertiliser and water it in well.

Young trees are usually vigorous growers that are not greatly troubled by pests and diseases, if problems do occur they can be treated just as you would a large shrub. However, large established trees are difficult to treat; they are often too tall safely get to the top of and effective coverage with sprays is all but impossible with domestic gardening equipment. Controlling pests and diseases in large trees is usually an area for professionals, they have the necessary equipment and expertise. No tree is worth covering yourself in pesticide or breaking your neck for. That said, most trees are worth the effort involved in trying to save them.

Tree Selection

The following list includes some of the more common garden trees, you will also find some trees or tree-like plants in the chapters covering palms, the Proteaceae and rhododendrons.

Each entry describes the foliage and flowers, the propagation requirements, any special climatic requirements and species with distinctive appearance or cultivation requirements. The following symbols and abbreviations are also used for each entry.

C or B denotes conifer or broadleaf.

E or D denotes evergreen or deciduous.

A figure, such as -20 denotes the approximate hardiness of the most tender common species in °C.

The height and width, eg 20 × 8, beside the symbol is the tree’s mature height, in metres, under average garden conditions. A mature tree is one that is about thirty to forty years old, which is about the normal life of a garden, extremely old trees may be considerably larger.

The rate of growth is indicated by the figure following the mature height and width, eg (4), it is the height, in metres, of the tree at five years old.

Abies
C/E/-20/30 × 15 (2.5)

This genus includes some very large trees, but most of the garden forms are among the more compact conifers. They are superb plants for high altitude gardens with all, except perhaps A. delavayii, hardy enough to tolerate most frosts. They have short, flattened needles arranged around or along the top of the branches. Many, especially A. concolor, have glaucous foliage. The cones, which are often tinted purplish-blue and dripping with resin, sit erect on the branches rather than hanging from them. Firs prefer a cool moist soil with ample summer water and rarely do well in hot and dry or very windy areas. The species may be raised from seed sown at 15°C, selected forms and hybrids are raised from summer cuttings.

Acacia
B/E/-8/6 × 6 (4)

A genus of about 1000 species mainly found in Australia and Africa. Those in gardens are virtually all Australian. There are three main foliage types: the sickle shaped leaf, typified by A. floribunda and A,. longifolia, the fine ferny leaf, such as that of A. cardiophylla, and the small triangular leaves seen in a few species, such as A. cultriformis and A. pravissima. All of the commonly grown species have fluffy yellow flowers, often in great abundance. The flowering season ranges from mid winter to summer, depending on the species. Acacias are colourful, easy-care plants best grown in light well-drained soil in full sun. Raise from seed sown at 18°C.

Acer
B/D/-25/10 × 6 (3)

The maples include a wide range of species from the Northern Hemisphere temperate region. A. platanoides has interesting tassel-like flowers but most maples are grown for their form and their foliage. The style of leaf varies but the typical palmate ‘maple leaf’ as depicted on the Canadian flag is common to most species. The leaf size ranges from less than 25 mm across to over 150 mm. The new spring growth often goes through several colour phases as it matures and many species and cultivars provide superb autumn colour. The most common garden species are the Japanese maple (A. palmatum), the Norway maple (A. platanoides), and the box elder (A. negundo). The many forms of A. palmatum are probably the best suited to small domestic gardens. However, they are prone to wind burn. Some species, such as A. griseum have interesting peeling bark. Species are raised from seed sown at 18°C, selected forms are grafted onto species stock.

Aesculus
B/D/-25/15 × 10 (3.5)

The horse chestnuts are not for small gardens. Both the common species, A. × carnea and A. hippocastanum, are deciduous trees that will grow to at least 15 m. They have deep green fan-shaped leaves up to 200 mm across. A. × carnea (particularly the form ‘Briotii’) has upright spikes of pink flowers in spring and is the more attractive of the two species when blooming. However, it is less widely planted than the white flowered H. hippocastanum, which has proved to be tougher and more adaptable. Both species have 50-75 mm diameter fruits enclosed in spiny capsules that can be messy. Horse chestnuts are most at home in park-like settings where they have the room to develop into stately specimen trees. They are best grown in deep moist soils. Species are propagated by stratified seed sown at 18°C, selected forms, are budded or grafted.

Agathis
C/E/-8/15 × 4 (2)

This genus includes about 15 species native to the Pacific region. The best known species is A. australis, the New Zealand kauri. Several species, such as the Queensland kauri (A. robusta) are, or have been, important timber trees. The kauri is now relatively rare in the wild although it is widely planted in parks and large gardens. Ancient trees are enormous with huge trunks and crowns, but garden specimens are unlikely to exceed 8m until many years after planting. The narrow, lanceolate, bronze green leathery leaves are up to 100mm long on young trees but only 40mm long on mature trees. The almost spherical cones are about 70mm diameter. Although naturally restricted to the northern North Island A. australis will grow as far south as Dunedin although it is very slow growing in southern areas. Kauris prefers moist humus enriched well-drained soil and ample summer water. Raise from seed sown at 20°C.

Agonis
B/E/-4/8 × 5 (4)

An Australian genus of about 12 species. The best known tree-sized species is the willow myrtle (A flexuosa). In general appearance it resembles a weeping eucalyptus. It is a broad headed tree with 125 mm long pendulous willow-like leaves and small, scented creamy white flowers in clusters in early summer. The flowers are showy, but the tree is mainly grown for its graceful growth habit. Apart from being somewhat frost tender it is easily grown in any sunny, well-drained position. It is usually raised from seed sown at about 20°C. The very attractive variegated is only rarely seen because it is difficult to propagate.

Ailanthus
B/D/-25/15 × 10 (7)

Tree of Heaven (A. altissima) is a very rapidly growing  tree with deep bronze green, pinnate leaves that are up to 600 mm long. The unspectacular greenish cream flowers, which appear in late spring, are followed in autumn by russet coloured winged fruit that is useful in dried arrangements. It is a tough, adaptable tree that tolerates drought, heat and air pollution once established and also has good autumn colour. Ailanthus will grow well in any deep moist soil. It may be raised from stratified seed sown at 20°C or from root cuttings.

Albizia
B/D/-12/7 × 8 (4.5)

The silk tree (A. julibrissin) is an excellent shade or lawn tree. It has a flat-topped spreading habit and large bipinnate leaves composed of many tiny leaflets that filter the sun well, they also rot down or blow away quickly when they fall in autumn. In summer it produces fluffy ball-shaped pale yellow and pink flowers. The form ‘Rosea’ has deep pink flowers. It thrives in light well-drained soil and is usually raised from seed sown at 22°C. Selected forms are sometimes propagated by autumn cuttings or by grafting.

A. lophantha is an evergreen species that closely resembles an acacia. It has bright, slightly glaucous, green pinnate leaves and 100mm long fluffy yellow bottle brush flowers. It grows rapidly to 7m x 4m and can become invasive as it self-sows freely. It is hardy to about -4°C.

Alder–see Alnus

Alectryon
B/E/-4/6 × 4 (2)

The New Zealand oak or titoki (A. excelsus) is the only commonly grown species. It is a densely foliage tree with glossy, mid green pinnate leaves up to 300mm long. The clusters of tiny flowers, which appear in late spring, are followed by brown seed capsules that split open to reveal a large black seed surrounded by a bright red fleshy pulp. The new growth, flower buds and seed pods are covered in a fine brown indumentum. Plant in cool, moist, well-drained soil. It is usually propagated by seed, which should be soaked and sown at 20°C.

Alnus
B/D/-15/15 × 8 (3)

Alders are ideal poorly drained areas but they can be a little too untidy for carefully maintained gardens. The common A. glutinosa may reach 30 m with great age. The leaves are about 75 mm long, deep green and coarsely toothed. In spring large woody catkins form, these can be messy when they fall. It is a rapid growing tree that tolerates very wet, even salty soil. A. rhombifolia has large toothed, nearly palmate, leaves that are deep green above and silvery grey on the underside. A. cordata, Italian alder has 100 mm long heart-shaped leaves. It is less upright than other alders and forms a good canopy. A. incana has slightly tomentose stems and leaves and is available in a yellow leafed form, ‘Aurea’. Apart from the selected foliage forms, which are grafted, alders are usually raised from seed sown at 18°C.

Araucaria
C/E/-4/15 × 6 (2)

This Southern Hemisphere genus is most commonly represented by the monkey puzzle tree (A. araucana), the Norfolk Island pine (A. heterophylla) and the bunya bunya (A. bidwillii). All are ultimately too large for small gardens, but they are attractive when young. They have deep green spiny foliage arranged radially around the branches and all develop large cones with edible nuts. These trees are very stiffly upright with a symmetrical branch structure that, in young trees, is almost perfect. A. bidwillii and A. heterophylla are superb coastal trees but A. araucana is best sheltered from salt winds. A. araucana is hardy to about -15°C, A. bidwillii to about -10°C once established, and A. heterophylla to about -4°C. They prefer moist well-drained soil, but will tolerate drought once established. Propagate by seed sown at 20°C.

Arborvitae–see Thuja

Arbutus  
B/E/-15/8 × 6 (2)

The strawberry tree (A. unedo) is so called because of its prominent warty red fruit that follow the spring and summer borne clusters of lily-of-the-valley-like flowers. The rounded, dark green red-stemmed leaves are about 60 mm long and finely serrated. The reddish brown bark is attractive too, especially when wet. The strawberry tree needs to be shaped when young to produce a neat tree. It is tolerant of coastal conditions and alkaline soil, which is unusual for an ericaceous plant. Grow in moist, well drained, humus enriched soil in sun or light shade. Raise from seed sown at 18°C.

Ash–see Fraxinus

Australian frangipani–see Hymenosporum

Azara
B/E/-15/8 × 5 (2.5)

The vanilla tree (A. microphylla) is a rather open growing tree with tiny rounded deep bronze green leaves and springtime clusters of small fluffy yellow flowers that are strongly vanilla scented. It is easily grown in most well-drained soils. A very attractive golden cream variegated form exists but is only rarely available. Propagate by seed sown at 18°C or by semi-ripe cuttings. A. lanceolata is a similarly sized species with larger lanceolate leaves and larger flower clusters that are not as highly scented as those of A. microphylla, nor is the tree as hardy. Other species such as the somewhat tender (-4°C) but highly fragrant A. dentata are seldom seen outside large public gardens.

Balsam fir–see Abies

Bay laurel–see Laurus

Bead tree–see Melia

Beech–see Fagus

Beilschmiedia
B/E/-4/8 × 4 (2.5)

This Southern Hemisphere genus includes two New Zealand natives, tawa (B. tawa) and taraire (B. tarairi), both of which are cultivated. Both are very upright trees with a dense foliage canopy. Taraire has rounded leathery leaves up to 140 mm long, they are deep green above and whitish below. Tawa has 100 mm long narrow leaves that are also whitish on the underside. The new growth of both species is covered in a fine brown indumentum. Both species have insignificant spring flowers that are followed by 30 mm long fleshy berries, those of taraire are black, while tawa has red fruit. Beilschmiedia prefers a moist well-drained soil. Propagate by seed sown at 20°C.

Betula
B/D/-30/10 × 6 (3.5)

So extensively planted that it is virtually an urban cliche the silver birch (B. pendula) and its close relatives are, nevertheless, attractive trees. Most of the species are very similar to one another, differing only in leaf size and minor growing details.

B. pendula is the most common and typical of the genus. It has 75 mm-long finely serrated pendulous, pointed oval leaves and peeling silvery bark that reveals the bright white new bark beneath. The spring flower catkins shed profusely and can be a nuisance. Other species, such as B. albo-sinensis, B. nigra, B. maximowiczii and B. papyrifera, vary in bark colour and leaf size but they are similar in general appearance. Birches grow in almost any soil and tolerates the most severe frosts. They are rather prone to aphid damage, which can lead to sooty mould. Most birches are raised from seed sown at 15°C, but selected forms are sometimes grafted.

Birch–see Betula

Brachychiton
B/D/-4/10 × 5 (2)

the Illawarra flame tree’ (B. acerifolia) has 200 mm wide leaves that are somewhat maple-like, although glossy and quite leathery. The deep red flowers are 25mm across and carried in large panicles that are extremely showy. The vivid flowers are made all the more conspicuous as the leaves around the flower heads fall just before blooming starts. It flowers in early to mid summer. The boat-shaped seed capsules that follow can be dried for use as floral decorations. Several other species are grown; the most distinctive is the ‘Kurrajong’ (B. populneus), which is upright with poplar-like leaves and growth habit. Hardier than B. acerifolia but its white flowers are not nearly as spectacular. Propagate by seed sown at 22°C.

Buttercup tree–see Cassia

Cabbage tree–see Cordyline

Camphor tree–see Cinnamomum

Cassia 
B/E/-34 × 4 (2.5)

A genus of over 500 species of shrubs and trees, many have been reclassified as Senna, but they are likely to be known as Cassia for many years. The most common species is C. corymbosa, particularly the form ‘John Ball’. It has bright green pinnate leaves that are up to 150mm long and composed of leaflets with prominent midribs. Yellow buttercup-like flowers in large clusters appear from about the middle of March. Grow in light well-drained soil in full sun. Most other species have a similar appearance but vary slightly in size, leaf shape and flowering season. C. tometosa is a shrubby winter-flowering species that may self-sow and become invasive. Except for ‘John Ball’, which is cutting grown, cassias are usually raised from seed sown at 22°C.

Catalpa
B/D/-25/10 × 8 (3.5)

The Indian beans are large trees that are surprisingly showy for such hardy plants. The two common species, C. bignonioides and C. speciosa, have pointed oval leaves that may be up to 250mm across. Heads of white, yellow and purple trumpet-shaped flowers appear in summer and are held well above the foliage. The flowers are followed by prominent seed pods. The yellow-leafed form of C. bignonioides known as ‘Aurea’ is an impressive tree even when not in flower. A purple-leafed hybrid is also occasionally sold. Plant in moist well-drained soil. Indian beans may be raised from seed sown at 20°C, but the selected foliage forms are grafted or budded.

Cedar–see Cedrus

Cedrus 
C/E/-20/15 × 12 (2)

Cedar is a genus of four species. Many magnificent specimens of the Atlas Mountain cedar (C. atlantica), the Himalayan cedar (C. deodara) and the cedar of Lebanon (C. libani) grace our larger parks and gardens, but the fourth species, the Cyprus cedar (C. brevifolia) remains rare. Cedars have wide spreading drooping branches that are densely clothed with clusters of fine needles. There are several selected foliage forms, the best known of which is the blue Atlas cedar (C. atlantica ‘Glauca’) Cedars have resinous egg-shaped cones which are held erect on top of the branches. The cones are quite a feature when young and green but lose their appeal as they age to dry brown husks. Cedars prefer moist well-drained soil, although they are drought tolerant once established. The species may be raised from seed sown at 18°C, but selected forms are usually autumn-cutting grown or occasionally grafted.

Celery pine–see Phyllocladus

Cercis
B/D/-25/8 × 5 (2)

Judas tree (C. siliquastrum) and Chinese redbud (C. chinensis) have similar foliage and flowers. Both have distinctive light bronze green heart-shaped leaves that are about 100 mm long. The flower clusters, which seem to sprout from every twig in spring, are an unusual shade of purplish pink. The flowers are followed by bean-like seed pods. White flowered forms are available. The foliage often colours well in the autumn. These trees are easily grown in most reasonably well-drained soils.

Other species seen occasionally are the very hardy Eastern redbud (C. canadensis) and the glaucous leafed Western redbud (C. occidentalis). All may be raised from stratified and soaked seed sown at 20°C. The selected forms of C. canadensis are usually budded but white forms of C. siliquastrum will come true to type if hand pollinated.

Chamaecyparis
C/E/-25/10 × 5 (2)

The most common species of this genus is the Lawson cypress (C. lawsoniana). The true species has somewhat drooping fan-like sprays of bright green cupressoid foliage, but it is available in an enormous range of cultivated forms that include ground covers, rockery dwarfs, columnar shrubs and trees. It also comes in a wide range of foliage types and colours. The other common species, C. nootkatensis, C. obtusa, C. pisifera and C. thyoides, while not quite so highly variable have, nevertheless, been developed into many widely differing forms. All are extremely tough plants that do well in cool, moist, well-drained soil. They are reasonably drought tolerant once established but are not at their best in hot dry areas. Except for farm shelter belts the true species are seldom grown. Most garden specimens are cultivars propagated by summer or autumn cuttings.

Chilean Fire Bush–see Embothrium

Cinnamomum  
B/E/-6/12 × 10 (1.8)

The camphor tree (C. camphora) has bright yellowish green to pink new growth and clusters of fragrant small yellow flowers. The flower clusters appear in late spring and are followed by tiny blackish fruits. The leaves are about 125mm long and deep glossy green when mature. Although classed as an evergreen, there is significant leaf fall in late winter and early spring. A sturdy strong growing tree with heavy branches and a dense root system that limit how close it can be positioned to paths, driveways or buildings. The bark is very attractive, especially when wet, and is also very aromatic. It is the source of camphor and camphor-wood. It is best grown in moist well-drained soil with ample summer moisture. Propagate by semi-ripe autumn cuttings or seed sown at 20°C. The ‘Nepal Camphor Tree’, C. glanduliferum, has larger leaves, a more upright growth habit, and is more frost tender.

Cordyline
B/E/-15/6 × 3 (1.8)

The native cabbage tree (C. australis) is a very widely grown. Young trees usually have only one trunk topped with a head of long sword-shaped leaves. As they mature basal shoots and new trunks often develop to create a clump of trunks. The basal shoots are sometimes removed from garden specimens, which leads to greater branching higher up and a tree-like shape. The fragrant small white flowers, which open from late spring, are massed on panicles up to 1 m long and are followed by small white berries. Several selected foliage forms, including the beautiful variegated ‘Albertii’, are available. Other species occasionally grown in domestic gardens include the ‘Mountain Cabbage Tree’ C. indivisa, which has much wider, somewhat glaucous, leaves with prominent ribbing. It is an attractive plant but demands moist soil and high humidity to be at its best. C. banksii is a multi-trunked shrub that flowers very heavily. C. stricta and C. terminalis are frost tender Polynesian species. C. stricta has lavender flowers and C. terminalis comes in many boldly variegated forms, which are often grown as house plants. Most species prefer moist soil and are quite tolerant of poor drainage. Usually grown from seed sown at 18–24°C, although selected foliage forms are propagated vegetatively, either by suckers or by using sections of the young stems as cuttings.

Cornus
B/D/-20/6 × 5 (1.8)

Dogwoods have simple but bold spring flowers, good autumn foliage colour, and some have brightly coloured winter stems. C. controversa, C. florida and C. kousa usually have the best flowers, while C. nuttalii provides brilliant autumn colour. C. alternifolia has a graceful tiered growth habit, but insignificant flowers. C. stolonifera has bright red winter twigs and C. capitata is evergreen with unusual fruit. Most species have simple pointed oval leaves about 125mm long and there are some attractive variegated forms. The flowers have four leathery petals and are usually white when first open but develop pink tints as they age. The flowers are often followed by large round fruits that are seen at their best on C. kousa and C. capitata. Most dogwoods are very hardy but C. capitata is often damaged at -6°C when young. They do best when planted in moist, humus enriched, well-drained soil in sun or light shade. The species may be raised from stratified seed sown at 20°C; hybrids and selected forms are grafted or grown from suckers or semi-ripe summer to early autumn cuttings.

Crab apple–see Malus

Crataegus
B/D/-25/6 × 5 (2)

Hawthorns have become uncommon due to a general move away from deciduous plants and because of their thorns, high susceptibility to fireblight and pear slug. Also, some people object to the smell of the flowers. Nevertheless, there are many attractive species and hybrids. They vary in leaf size, flower colour and the colour and size of the fruit. English hawthorn (C. laevigata [oxyacantha]) has 50 mm-long three lobed leaves and small white to pale pink flowers that are followed by bright red fruit. Many selected forms of this species, and the very similar C. monogyna, have been produced. There are white, pink and red flowers, both single or double. The doubles do not set much fruit but are more attractive when in flower. Other common species include the glossy leafed C. phaenopyrum and C. crus-galli, which is also noted for its autumn colour. Hawthorns are tough, adaptable plants that will grow in most conditions but they are best suited to areas with cold winters. The species may be raised from stratified seed sown at 18°C, but selected forms are usually grafted onto species stock.

Crepe myrtle–see Lagerstroemia

Cryptomeria  
C/E/-20/20 × 8 (2.5)

The Japanese cedar (C. japonica) is a large pyramidal tree with horizontal branches that droop at the tips. The soft needle-like foliage is bright mid green in summer turning to rich purplish brown in winter. The cultivated forms range from tiny rockery dwarfs to large shrubs. Their foliage often differs from the parent species with varying size and density of needles. The species has small reddish brown cones, but many of the cultivated forms appear to be sterile or rarely produce strobili. Japanese cedars are best grown in cool moist well-drained soil. The species may be raised from stratified seed sown at 18°C; the selected forms are usually cutting grown.

Cupressocyparis
C/E/-25/20 × 8 (3)

Leyland cypress (C. leylandii) is a bi-generic hybrid between Chamaecyparis nootkatensis and Cupressus macrocarpa. Early examples are now over 30 m tall, but as it has only been in existence for about 100 years its absolute size is unknown. Because it is so rapid growing, extremely hardy, and tolerant of most soil conditions, including periods of poor drainage, it has become popular for shelter belts. Leyland cypress will withstand regular hard trimming and has also been grown as a timber tree. The foliage is typically cupressoid and composed of flattened sprays. Several forms with varying foliage and growth habit have been selected. ‘Leighton Green’ is the best known. It has very bright green foliage and a somewhat more open branch structure. Propagate from heeled cuttings, which may be taken at any time.

Cupressus
C/E/-12/15 × 12 (3)

Monterey cypress (C. macrocarpa) covers thousand of kilometres as farm hedgerows and windbreaks. It has sprays of deep green foliage composed of flattened whippy stems clothed in tiny adpressed scale-like leaves. Many selected forms have been developed so that a huge range of sizes and foliage types is now available. These range from tiny dome shaped rockery plants through to large trees. The golden forms of C. macrocarpa are among the best and brightest yellow foliaged conifers.

The pencil cypresses (C. sempervirens forms), particularly the very narrow forms ‘Stricta’ and ‘Gracilis’ and the yellow-foliaged ‘Swane’s Golden’, are popular for flanking entrance ways and avenues. They add a stark upright element that is useful for breaking a predominantly horizontal design. Although hardy C. sempervirens is a poor choice for areas that experience regular snowfalls: the weight of the snow bends the branches outwards and destroys the shape.

Other species commonly grown include C. arizonica and C. glabra; their tendency towards glaucous foliage has enabled the development of blue conifers that are very tolerant of drought and poor soil. C. cashmeriana and C. funebris are large species with drooping foliage sprays on horizontal branches that move gracefully in the breeze.

Most species have small resinous spherical cones of about 40mm diameter. C. cashmeriana is not reliably hardy below -12°C but all the other species tolerate -15 to -20°C. The species may be raised from stratified seed sown at 18°C, but the cultivated forms must be propagated vegetatively, usually by cuttings.

Dacrydium
C/E/-15/15 × 5 (1.8)

Rimu (D. cupressinum) is a graceful native conifer with a silhouette that is impossible to mistake for any other tree, especially when young. Until is reaches about 10 m high, rimu has a weeping conical habit, as it matures it develops into a columnar tree. The branches are clothed in very short, stiff, bronze-green needles, which are  green in spring and summer turning to reddish brown in autumn and winter. The effect is similar to that seen in Cryptomeria japonica. The bright red drupes with protruding black seeds are unusual, but seldom occur in large enough numbers to be a feature. There are several other cultivated species: D. bidwillii resembles a very small D. cupressinum, it grows to about 2.5m high. The Huon pine (D. franklinii) is a Tasmanian native that is similar to D. cupressinum. Rimus are hardy to about -15°C. They are best in a cool but humid climate with moist, humus enriched well-drained soil. Rimus are usually propagated by stratified seed sown at 18°C; small cuttings will strike roots, but they are not very reliable.

Dawn redwood–see Metasequoia

Dogwood–see Cornus

Elaeocarpus
B/E/-8/8 × 5 (2)

Two species are seen in gardens: one Australian (E. reticulatus, blueberry ash) and the other a New Zealand native (E. dentatus, hinau). Both have deep green leathery leaves that are about 100 mm long with serrated edges and bear racemes of small, pendulous, creamy white flowers. Those of E. reticulatus are finely fringed at the edges. Both species have small purplish-blue berries. E. dentatus is the taller of the two species, it will also withstand more frost than E. reticulatus. Both trees appreciate moist, humus-enriched, well-drained soil in sun to moderate shade with ample summer moisture. Raise from seed sown at 18°C or semi-ripe cuttings.

Elm–see Ulmus

Entelea
B/E/-2/5 × 3.5 (3.5)

Whau (E. arborescens) is a native tree with light green heart-shaped to three lobed leaves that can be up to 200 mm across. It is a small tree that rarely exceeds 5m x 3.5m. In late spring it produces massed clusters of white anemone-like flowers, which are followed by bristly seed capsules. It is easily grown in any moist well-drained soil in sun or light shade, provided it is sheltered from frost. Whau becomes untidy with age and if pruned its pithy stems tend to die back. However, as it grows very quickly and is easily propagated from spring sown seed there is no difficulty in establishing new plants.

Eucalyptus
B/E/-1 – -15/15 × 6 (4)

This large genus of over 600 species is almost exclusively Australian and is the characteristic feature of that country’s flora. The typical gum tree has peeling bark and sickle shaped glaucous green leathery leaves somewhere between 75mm and 150mm long. The fluffy filamentous flowers, which may be any shade of white, cream, pink, yellow, orange or red, vary in size and season. Some, such as E. ficifolia, put on a truly magnificent floral display while others, such as E. nicholi, have insignificant flowers.

Eucalypts range in size from the snow gum, E. niphophila, at around 6m to giants, such as E. globulus, which may exceed 60m. Although most species eventually develop the familiar sickle-shaped leaves, some have juvenile leaves that envelop the stem, the silver dollar gum (E. polyanthemos) effect. Gums also vary in their hardiness, some are almost totally intolerant of frost while others can withstand -15°C.

Many gardeners reject eucalypts because of their rapid growth, leaf and bark litter, and potentially large size. However, they are among the most attractive and easy care evergreen trees available. Plant in light well-drained soil in full sun and water well in summer until established. Eucalypts are attacked by a wide range of pests, such as scale, tortoise beetles, weevils and leaf roller caterpillars but in most cases they outgrow the problems. Raise from seed sown at around 20°C; specialist suppliers offer a huge range of species.

Eucryphia
B/E/-12/8 × 3.5 (2)

This genus is composed of several large shrubs or small trees native to Chile and Australia. The species most widely grown is E. cordifolia, a Chilean native. The other Chilean species, E. glutinosa, is rarely seen in gardens but has been crossed with E. cordifolia to produce the hybrid E. × nymansensis. The three Australian species, E. milliganii, E. moorei and E. lucida are rarely seen. All the species have similar anemone-like white flowers that appear in spring but they vary in foliage and size. E. cordifolia has 75mm long deep green serrated edged oval leaves with silvery undersides. E. glutinosa has mid green serrated edged pinnate leaves composed of five leaflets. E. moorei has mid green smooth edged pinnate leaves composed of seven leaflets while the other two Australian species have small oval leaves. E. × nymansensis has foliage with the colour of E. cordifolia and the form of E. glutinosa. It has larger flowers than any of the species. As with many choice Chilean plants it grows best in a cool moist climate, such as that of coastal Otago or Southland. The species may be raised from seed sown at 18°C, but the hybrids are propagated by semi-ripe cuttings.

Fagus  
B/D/-30/12 × 10 (2.5)

The European beech (F. sylvatica) is a large widespreading tree that is unsuitable for small gardens. The true species is seldom seen, instead several cultivated forms are grown. All except the cut leafed ‘Laciniata’ have similar 100mm long deeply ribbed rounded leaves. However, the foliage colour varies considerably from golden, variegated and tricolour variegated forms to the purple and blackish purple forms, such as ‘Riversii’, that are commonly known as copper beeches. There is also a very upright growing variety called ‘Fastigiata’. These easily grown trees tolerate most soils although they seldom grow well in coastal conditions. The species and some of the purple leafed forms may be raised from stratified seed sown at 18°C; the best selected forms are usually grafted. Other species, such as the larger leafed American beech (F. grandifolia), are occasionally seen in parks and larger gardens.

False acacia–see Robinia

Ficus
B/E/-1 – -10/7 × 5 (2.5)

Many of the evergreen Ficus species that are often used as house plants are hardy enough to be grown outdoors in mild areas. Of these the toughest are F. elastica (-3°C), F. macrophylla (-3°C), F. rubignosa (-4°C) and F. benjamina (-2°C). However, even if these species survive the winter they require warm summer conditions to grow well. All of these species will eventually become large, widespreading trees with rounded leathery leaves that are often very large and glossy. The common edible fig (F. carica) is hardy to about -10°C. It is a deciduous tree that is often espaliered. Valued for its edible fruit and its boldly lobed palmate leaves it grows well in most areas provided it gets as much sun as possible. Good fruit can only be expected in areas with reliably warm summers. Grow in moist well-drained soil in full sun. The species may be raised from seed sown at 22°C, semi-ripe cuttings or aerial layers.

Fig–see Ficus

Flowering almond–see Prunus

Flowering cherry–see Prunus

Fraxinus 
B/D/-20/12 × 7 (3.5)

Ash is a Northern Hemisphere genus of some 65 species of shrubs and trees. The common F. oxycarpa is a broad headed deciduous tree that is frequently used as a street tree. It has 200 mm long pinnate leaves usually made up of seven leaflets. In spring the plant is covered in panicles of tiny fragrant white flowers. In autumn the foliage develops rich purple and gold tones. Several forms, the most common of which is the claret ash, ‘Raywoodii’, have been selected for their autumn foliage colour.

The European ash (F. excelsior) is also widely grown. It has slightly larger leaves composed of 7-11 leaflets that develop little or no autumn colour. However, the form ‘Aurea’ and the pendulous ‘Aurea Pendula’ have bright yellow autumn leaves. F. excelsior is available in several growth forms; upright, round headed and pendulous.

The third common species is the manna ash (F. ornus). This species has a dense foliage cover and large flower heads. It colours well in the autumn. F. mariesii is similar.

The species may be raised from stratified seed sown at 18°C, but selected forms are usually grafted onto F. excelsior stocks. Specialist seed suppliers stock many species including the near-evergreen F. uhdei.

Giant redwood–see Sequoiadendron

Ginkgo 
C/D/-25/15 × 10 (3)

The maidenhair tree’ (G. biloba) is the sole survivor of a group of plants that once dominated much of the earth’s surface. Its light to mid green leaves are shaped like the individual pinna of a maidenhair fern frond and give the tree an appearance quite unlike that of any other conifer. In autumn the leaves turn a bright yellow before falling and this colour is one of the tree’s main attractions. Forms selected for better colour are occasionally available. Female trees bear soft round fruit that is has an unpleasant scent when squashed, so if possible, plant only male trees. Ginkgo will grow in most soils and conditions but it is best with ample summer moisture. Trees may be raised from stratified seed sown at 22°C, but the only way to be sure of getting a male plant is to graft or take cutting material from a tree of known sex.

Golden chain tree–see Laburnum

Golden-rain tree–see Koelreuteria

Gum–see Eucalyptus

Hawthorn–see Crataegus

Hinau–see Elaeocarpus

Hoheria
B/E or D/-10/12 × 4 (3)

This New Zealand genus includes some of the few native deciduous trees. They are commonly known as ribbonwoods or lacebarks because of the fine filigree of bark that underlies the surface bark. The most common species is the evergreen H. populnea. When young it is a very upright tree, at it ages it becomes more round-headed. It has 75-125 mm long, quite heavily veined, pointed elliptical leaves with serrated edges. ‘Variegata’ is a form with leaves that have a large central yellow blotch, ‘Alba Variegata’ has a broad white margin, ‘Osbornei’ has a purple reverse to the leaf and flowers with purple stamens, and ‘Purpurea’ has leaves with deep purple undersides. All of the varieties produce massed small clusters of 2 cm diameter white flowers in late summer and early autumn. Other evergreen species grown include H. sexstylosa, which is very similar to H. populnea, and H. angustifolia, a 6 m high species that has very narrow leaves and small flowers.

The two deciduous species, H. lyalli and H. glabrata, are similar to one another. H. lyalli grows to about 7 m while H. glabrata is a little taller at 9 m. The leaves are similar to the common H. populnea but are covered in fine hairs. H. glabrata has somewhat glaucous leaves. Both of these species flower in summer and are hardy to at least -15°C. All the species grow best in moist, humus enriched, well-drained soil in sun or light shade. They may be raised from seed sown at 18°C, but the selected foliage forms must be propagated vegetatively.

Holly–see Ilex

Horse chestnut–see Aesculus

Hymenosporum 
B/E/-6/8 × 5 (3)

The Australian frangipani (H. flavum) is more closely related to Pittosporum that the true frangipani (Plumeria rubra). It has 125 mm long glossy, deep green, pointed elliptical leaves that tend to be clustered at the ends of the branches. The terminal clusters of deep yellow flared trumpet to stellate flowers have a sweet scent. They may occur at any time but are most abundant in spring and early summer. Australian frangipani requires moist well-drained soil and a position in full sun or very light shade. Usually raised from seed sown at 22°C or by semi-ripe cuttings.

Ilex  
B/E/-15/6 × 4 (2)

The common holly (I aquifolium) is widely recognised as a symbol of Christmas. The true species is seldom grown, except as hedging, instead selected forms or hybrids, such as I. × altaclarensis, with varying foliage shapes and colours and various berry colours, are planted. Only female plants set fruit, which is an advantage in some cases as the fruit can be messy. If desired, self fertile plants are available. Sizes vary but most hollies are large shrubs or small trees. Several other species are also grown. Some, such as I. cornuta, are very like I. aquifolium but others, such as I. crenata have small smooth rounded leaves and are excellent low hedging plants. Plant holly in moist well-drained soil with sun to moderate shade. The species may be raised from stratified seed sown at 18°C, but hybrids and selected forms are grown from semi-ripe cuttings.

Illawarra flame tree–see Brachychiton

Jacaranda  
B/D/-5/12 × 8 (3)

Only one species of this genus of 40 is widely grown. J. mimosifolia is common in milder areas and is sometimes used as a street tree. It is a semi-evergreen or deciduous tree that is almost totally frost tender when young, but tolerates -5°C once well established. The very finely divided fern-like bipinnate leaves may be up to 300 mm long. Jacaranda is mainly grown for its spectacular clusters of bright purplish-blue trumpet flowers; these may appear in spring in very mild areas, although summer is the main flowering season. White and pink flowered forms are occasionally available. This tree needs warm temperatures to flower well. Jacaranda does best in moist well-drained soil in full sun. Usually raised from seed, which should be soaked, and sown at 24°C.

Japanese cedar–see Cryptomeria

Judas tree–see Cercis

Kamahi–see Weinmannia

Kauri–see Agathis

Koelreuteria
B/D/-15/10 × 7 (2.5)

The golden-rain tree (K. paniculata) is by far the most common species of this genus but the Chinese flame tree (K. bipinnata) is also grown. Both have pinnate leaves that may be as much as 50 cm long. The foliage tend to be among the last to fall in autumn and often turns a bright yellow before dropping. In summer, both species have large terminal heads of yellow flowers that are followed by clusters of papery seed capsules. Those of K. paniculata are usually a light brown but the capsules of K. bipinnata take on many shades of pink orange and red, hence the name flame tree. Koelreuteria will grow in most soils and can withstand high alkalinity, as well as being very heat and drought tolerant once established. Usually grown from stratified seed, which should be soaked, and sown at 20°C.

Kowhai–see Sophora

Laburnum
B/D/-30/7 × 4 (3)

These well-known spring-flowering trees are now somewhat unpopular because of their untidy appearance after flowering. The true species are rarely seen, most garden specimens are either L. x vossii or L. x watereri, which are hybrids between L. alpinum and L. anagyroides. The soft green trifoliate leaves are attractive when young but tend to brown quickly and fall very early. Laburnum is commonly known as golden chain tree because of the long pendulous racemes of yellow sweet pea-like flowers that appear in spring. These flowers are followed by long seed pods, which are best removed as they are untidy and a drain on the plant. They are also full of extremely poisonous seeds. Laburnums are easily grown in almost any moist well-drained soil. As most of the garden forms are hybrids they are usually propagated vegetatively by open ground winter hardwood cuttings.

Lacebark–see Hoheria

Lagerstroemia
B/D/-6/6 × 4 (2)

The crepe myrtle (L. indica) is a beautiful heavy flowering small tree that needs consistent summer heat to flower well. Although deciduous it is not particularly hardy, being damaged at about -6°C. The simple glossy deep green oval leaves are about 60 mm long and are usually carried in groups of three. The 150–300 mm long terminal flower clusters, which appear in summer, are composed of many 30 mm diameter frilly flowers. There are many colour forms in shades of white, cream, pink, mauve and red; there are also dwarf forms suitable for tub cultivation. Grow in well-drained soil in full sun and water well in summer. Usually grown from semi-ripe cuttings under mist or by winter hardwood cuttings.

Lagunaria
B/E/-3/8 × 3.5 (2.5)

The Queensland hibiscus (L. patersonii) is not a hibiscus but does belong to the same family; the Malvaceae. Quick growing when young, it slows considerably after reaching 4 m. It has mid green leathery oval leaves about 75 mm long with silvery grey undersides. The 40-50 mm diameter mid pink mallow-like flowers are followed by 5-sectioned seed pods that contain irritant hairs. Remove the pods before they ripen unless you want to collect the seed. Queensland hibiscus is easily grown in most well-drained soils and is a good coastal tree. It is usually raised from seed sown at 20°C but will also grow from semi-ripe autumn cuttings.

Larch–see Larix

Larix  
C/D/-35/15 × 5 (3)

The larch (L. decidua) is one of the few deciduous conifers. It has bright to deep green needles in whorls along the stems. In autumn the needles become a bright yellow before slowly turning brown and falling. The squat cylindrical cones mature quickly and are usually seen fully open. This extremely hardy tree needs a climate with a distinct winter and grows well in high altitude areas. Larches do best in cool moist well-drained soil. The genus includes around a dozen species and several hybrids but the only one other, the hybrid L. x eurolepis, which is a cross between L. decidua and L. leptolepis, is at all common. It is a quick growing, somewhat glaucous tree with a profusion of warm brown cones and a slightly weeping open growth habit. Other species are available from specialist seed suppliers. The species are raised from stratified seed sown at 18°C; the selected forms should be grafted.

Laurus 
B/E/-10/7 × 3.5 (2)

The bay laurel (L. nobilis) does double duty as a classic culinary herb and a first rate garden specimen. It is not the only species of the genus but is by far the most common. While ultimately a large tree, it is able to be comfortably kept to 5 m x 2 m by regular trimming. The deep pointed oval leaves are up to 100 mm long with wavy edges. They are, of course, very aromatic when crushed. The small yellow flowers, which appear in mid spring, are relatively insignificant and are followed by small blackish berries. However, this is primarily a foliage tree and often used as a tub or topiary specimen. It may also be used for hedging. Laurel performs best in moist well-drained soil but will withstand drought. It is usually propagated by semi-ripe late summer or autumn cuttings.

Lawson cypress–see Chamaecyparis

Leyland cypress–see Cupressocyparis

Libocedrus
C/E/-12/8 × 2.5 (1.8)

This genus includes several New Zealand species. They are not widely grown in gardens but are quite frequently planted in parks and reserves. The best know is L. bidwillii, which is a columnar sub-alpine tree with light green cupressoid foliage carried in fern-like sprays or plumes. L. plumosa is a similar but larger species with larger foliage sprays. The New Zealand cedars prefer cool moist soil and semi-shade when young. They may be raised from seed sown at 18°C or by semi-ripe early autumn cuttings.

Lime–see Tilia

Linden–see Tilia

Liquidambar
B/D/-25/12 × 4 (2.5)

L. styraciflua is among the most spectacular of all the autumn foliage trees; it could easily be mistaken for a maple as the leaves are the typical palmate maple leaf shape and about 100–150 mm across. In the autumn the leaves develop magnificent yellow, orange, red and purple tones before falling. In mild areas it does not colour well and may be almost evergreen. However, variegated and other coloured leaf forms are available. Liquidambars also have very distinctive corky bark. The flowers are insignificant but the fruit that follows in autumn is conspicuous if not particularly attractive. Grow in a sunny position with moist well-drained soil. Forms selected for superior foliage colour are grown from winter hardwood cuttings, grafted or budded, however most seedlings will colour well. Other species sometimes grown include L. formosana, which has fairly smooth bark and generally does not colour as well in autumn, and L. orientalis, which is a smaller tree with smaller leaves.

Liriodendron
B/D/-30/12 × 8 (1.8)

The tulip tree (L. tulipifera) belongs to a genus of two species that is closely related to Magnolia. The leaves are an unusual shape, deeply lobed with a notch where the leaf tip would normally be. They are about 125-150 mm long and light green turning to bright yellow in autumn. There is a variegated form with a broad cream margin called ‘Aureo Marginatum’. The tulip-like yellowish green orange-based flowers appear in late spring. Viewed off the tree they are attractive but are usually so far up in the branches that they are all but invisible. The tulip tree is easily grown in any moist well-drained soil. Selected forms, such as the columnar ‘Arnold’ are budded or grafted. Seed, which should be stratified and sown at 20°C is not popular as seedlings do not flower reliably until they are at least 10 years old, while vegetatively propagated plants flower at 3-4 years old.

Macrocarpa–see Cupressus

Magnolia 
B/E or D/-20/12 × 8 (2.5)

This genus includes deciduous, semi-deciduous and evergreen trees and shrubs. Most of the deciduous species have the large cup-shaped flowers typified by the best known species, M. soulangiana. They have simple leathery oval leaves that may be up to 200 mm long or larger in the case of M. macrophylla, which has 300-600 mm long leaves. Those of the evergreen M. grandiflora are a glossy mid olive green on top with rust coloured felting below. Forms such as ‘Ferruginea’ have very heavy indumentum. Some of the smaller species, such as M. stellata, are really large shrubs but many magnolias become substantial trees. M. campbellii may grow to 20 m x 12 m. It is also one of the earliest to flower, usually starting in mid to late August.

Except for the unusual yellow-flowered M. acuminata and its hybrids there is not a wide range of flower colours, only white, pink, mauve and purple shades. However, the flowers are often very large. Those of the New Zealand hybrid ‘Mark Jury’ are up to 200mm across and those of M. macrophylla may be up to 300 mm in diameter. Of course flowers that size need protection from the elements and may not be practical for many gardens. The flowers, which in most species appear in spring and early summer, are usually followed by seed heads. M. grandiflora is less seasonal in its flowering and may even have a few flowers in winter in very mild areas. A few species, such as M. tripetala, have reasonably attractive seed heads. Some magnolia flowers have a fragrance, which can vary from a slight scent to a very heavy fragrance. The most common scented magnolias are M. grandiflora, M. heptapeta and M. sieboldii.

Plant magnolias in moist, humus enriched well-drained soil in sun or very light shade. By careful pruning to shape when young it is possible to produce wide spreading shrub-like growth or a single trunked tree as desired. The species may be raised from seed but they will not bloom for several years. The exact time varies with the species. M. loebneri will flower in 3 years from seed but M. campbellii may take 20 years. Hybrids and selected forms are grown from summer to autumn cuttings, budded or grafted.

Maidenhair tree–see Ginkgo

Malus  
B/D/-30/7 × 7 (2)

Crab apples are attractive, heavy flowering small to medium sized trees. However, they are perhaps too wide spreading and untidy, in terms of leaf and fruit drop, for small gardens. The leaves are elliptical and about 75 mm long, they are virtually identical to the common fruiting apples and subject to all the same diseases; leaf curl, mildew, etc. In spring the trees are covered with blossom. The flowers are followed by the conspicuous small apples that remain well into winter. Many species and hybrid forms are grown overseas but relatively few are available here. There is good range of flower colour but most have red fruit. Among the best are the ever-popular ‘Jack Humm’, which has long-lasting bright red fruit, M. ionensis ‘Plena’, which has large semi-double pink and white blooms, and ‘Oporto’, which has deep pinkish-crimson flowers and purple foliage. Grow crab apples in moist well-drained soil in full sun. The species may be raised from stratified seed sown at 18°C but hybrids are usually grafted.

Maple–see Acer

Maytenus
B/E/-15/8 × 6 (2.5)

The Chilean mayten (M. boaria) is an attractive evergreen tree that resembles a small weeping willow. When mature it is a handsome broad-headed tree with drooping branches that are densely clothed in small, bright green, finely toothed, lanceolate leaves. When young it is more upright and narrow. The flowers and fruit are insignificant. It is easily grown in most well-drained soils and may be raised from seed sown at 18°C. However, it is usually grown from semi-ripe summer and autumn cuttings. Mayten can self-sow and may become invasive in untended areas, but it is not difficult to control.

Melaleuca
B/E/-6/8 × 5 (2)

This Australian genus includes about 140 species of evergreen shrubs and trees. Most have tiny, often adpressed, needle-like or elliptical leaves. The flowers are similar to those of the closely related bottlebrush (Callistemon sp.) but are usually smaller. They are often followed by woody seed capsules that surround the stem in the same way that those of the Callistemon do. There are species in almost every colour of flower but cream, yellow, pinkish mauve and red predominate. Many species benefit from regular pruning to shape while others look better thinned to expose their branch structure. Most are extremely adaptable, withstanding drought, alkalinity, high salt content, low fertility and occasional waterlogging. They also tolerate coastal conditions but relatively few are hardy below -6°C. Best grown in light, yet moist, well-drained soil in full sun. Melaleucas are usually raised from seed sown at around 20°C, but they are also easily propagated by semi-ripe summer and autumn tip cuttings.

Melia
B/D/-10/8 × 4 (2)

The bead tree (M. azedarach) has finely cut luxuriant deep green bipinnate leaves that may be up to 600 mm long. In early summer it develops terminal panicles of fragrant lilac flowers. The fruit that follows is a hard 12 mm diameter yellow berry. If left untouched by birds they will remain on the tree after the leaves have fallen. The foliage develops little autumn colour. It is a hardy tree, but it requires shelter from the wind to protect the large leaves from damage. Plant in any well-drained soil. Usually raised from seed sown at 20°C, established plants may self-sow.

Metasequoia
C/D/-20/15 × 6 (2.5) 

The dawn redwood (M. glyptostroboides), rediscovered in China in 1945 after being thought extinct, is the sole surviving species of a very ancient genus that once dominated the world’s forests. It has fine light green 75 mm long pinnate leaves composed of narrow straight-sided leaflets. Although the foliage reddens in autumn before falling it does not develop the intense colour of the swamp cypress (Taxodium distichum), which it superficially resembles. Grown for its bright green new growth, rugged red bark and graceful growth habit, this is a tree for large gardens. Dawn redwood is usually raised from stratified seed sown at 20°C, but will also grow from semi-ripe summer cuttings.

Meryta 
B/E/-2/6 × 3.5 (2)

The foliage of the puka or pukanui (Meryta sinclairii) is among the most spectacular of any of our native plants. It has large deep green leathery oval leaves that may be up to 350 mm long. A cream variegated form is occasionally available. The panicles of greenish white spring and early summer flowers and the blackish fruit that follows are conspicuous but not particularly attractive. However, this is primarily a foliage tree. Very frost tender when young, it can withstand light frosts once established. In colder areas it makes a good house plant. Outdoors, plant in moist, humus enriched, well-drained soil in light to moderate shade. It will grow in full sun but the foliage tends to look bleached. Usually raised from seed sown at 20°C; the variegated form must be grown from semi-ripe summer or autumn cuttings.

Metrosideros
B/E/-3/8 × 8 (2)

The pohutukawa (M. excelsa) is the best known of this South Pacific genus of evergreen trees, shrubs and vines. From mid November it becomes a very conspicuous feature of many of our coastal gardens as its clusters of intense deep red filamentous flowers begin to open. The simple rounded leaves are a bright glossy mid green on young plants but mature trees have deep green leathery leaves with white indumentum. Old trees often develop aerial roots on the trunk and branches. Various flower colours and leaf forms are available. Except for being frost tender, especially when young, this is an easily grown tree. It tolerates most soils and is particularly well suited to coastal conditions.

Several other species are also grown. Those from the Kermadec Islands, Tahiti and other Pacific islands tend to be too frost tender to be grown outdoors in many areas but they are very effective tub plants for frost-free conservatories. The southern rata (M. umbellata) and the northern rata (M. robusta) are far tougher plants but they seldom do well in gardens. They have flowers that are similar to the pohutukawa but they are more inland, or sub-alpine, plants. Both species are hardy to at least -10°C so they are worth trying in areas too cold to grow M. excelsa. They grow very slowly and may take many years to flower from seed. All Metrosideros species grow well from seed sown at around 20°C; the selected forms must be propagated vegetatively, usually by semi ripe summer or autumn cuttings, or by removing pieces with aerial roots from mature plants.

Michaelia
B/E/-8/6 × 3 (2)

This genus is closely related to Magnolia and the two common species, M. doltsopa and M. figo, could easily be mistaken for small-flowered magnolias. Both have mid green leathery oval leaves about 100-150 mm long. M. doltsopa is the larger of the two species, it may grow to 10 m high, while M. figo rarely exceeds 5m. Both species flower in spring. M. figo is known as the port wine magnolia because of the fruity scent of its cream flushed purple 75 mm diameter cup-shaped flowers. M. doltsopa has larger (125-175 mm diameter) but similarly shaped creamy white flowers that have a delicate scent. Several hybrid forms have become available in recent years. Grow in moist, humus enriched, well-drained soil in sun or light shade, frost protection may be necessary for young plants. The species may be raised from seed sown at 20°C or by semi-ripe cuttings. Hybrids must be propagated vegetatively. Specialist seed suppliers sometimes stock less common species.

Monkey puzzle–see Araucaria

Moreton Bay fig–see Ficus

New Zealand oak–see Alectryon

Norfolk Island pine–see Araucaria

Nothofagus 
B/E & D/-15/15 × 8 (2)

Because of their large ultimate size southern beech species are seldom grown in domestic gardens, but they are sometimes seen in large parks and reserves. The genus includes about 20 species of evergreen and deciduous trees native to the temperate regions of South America (primarily Chile), Australia and New Zealand. Many of the plants seen gardens are New Zealand natives. The three main species (all evergreen) are red beech (N. fusca), silver beech (N. menziesii) and black beech (N. solandri). All develop into large trees with rounded foliage canopies, although they may be rather columnar when young. Most have small rounded leaves with serrated edges but N. solandri has tiny smooth edged leaves. N. fusca is probably the best choice as a garden specimen because of its bronze foliage tones. All species are subject to attacks by scale insects and aphids, which lead to sooty mould. Grow in cool moist soil. Usually raised from seed sown at around 15°C; selected forms can be propagated from semi-ripe tip cuttings taken in late summer and autumn. The Australian beeches are rarely grown but in recent years there has been some interest in the Chilean species.

Nyssa
B/D/-25/12 × 6 (1.8)

The tupelo (N. sylvatica) is a grown primarily because of its magnificent autumn colours and its ability to grow in very poorly drained conditions that would kill many other plants. It has a twisted and contorted stem and branch structure that is clothed from spring to autumn in simple, slightly glossy, rhomboidal mid green 100 mm-long leaves. In autumn the foliage develops intense fiery orange, red and yellow tones before falling. The spring flowers are inconspicuous but are followed in late summer and autumn by small blackish olive-like fruits. It is easily grown in most soils and usually raised from stratified seed sown at 20°C. N. aquatica is a similar species that, as the name suggests, tolerates very wet conditions and will even grow in a few inches of water.

Oak–see Quercus

Olea
B/E/-12/8 × 10 (2)

The olive (O. europaea) is one of the world’s most important commercial crops, while at the same time being a beautiful ornamental specimen. Old trees, and they can live to a great age, develop twisted and contorted branches of magnificent character. The 75 mm-long narrow leaves are deep green and leathery with silvery grey undersides that are often seen to great effect as the branches droop when wet with rain. The small panicles of tiny white flowers that appear in late spring are insignificant, but they are, of course, followed by the bright green fruit, which turns black late in the season just before dropping.

Olives are beautiful trees but they do create a litter problem. Fallen leaves and fruit can range from a nuisance to a constant chore. For this reason they are best located away from paths and driveways. In recent years much work has gone into selecting superior fruiting strains and even non-fruiting forms are sometimes available. Plant in light, yet moist, well-drained soil. May be raised from seed sown at 20°C, but most plants are grown from semi-ripe summer and autumn cuttings.

Olive–see Olea

Paulownia
B/D/-15/12 × 8 (4)

This is a Chinese genus of about half a dozen very quick growing deciduous trees. P. tomentosa is the species generally grown as a garden specimen. It is probably the hardiest of the genus, tolerating temperatures down to -15°C or even lower if protected when young. It is strongly branched tree with large (up to 300 mm long) leaves are heart-shaped tapering to a point at the tip, deep green on the upper surfaces and light green underneath with some felting. As it is impossible to keep a tree of this size out of the wind, it is inevitable that the foliage will suffer some damage. The flowers open in spring from the terminal heads of furry brown buds that are carried right through winter and late frosts may damage the developing buds. The flowers are spectacular purplish-blue trumpets carried in foxglove-like heads. They are followed by rounded seed capsules that hang on well into winter. Trees often carry the current year’s seed capsules and the following season’s buds at the same time. Plant in moist, well-drained soil. Usually raised from stratified seed sown at 22°C.

Pencil cypress–see Cupressus

Pepper tree–see Schinus

Phebalium
B/E/-8/5 × 1.5 (2.5)

Although this genus of evergreen shrubs and trees includes a New Zealand native, P. nudum, the species commonly grown in gardens, P. squameum, is Australian. The 75 mm long narrow leaves are deep green on the upper surfaces and light green to silvery grey underneath. The yellow and green variegated form known as ‘Illumination’ is very popular. The small starry cream flowers, which appear in early summer are conspicuous but not particularly showy. Phebalium is most commonly grown as a hedging or screening plant because its very narrow upright habit reduces the need for trimming. It is easily grown in most light, well-drained, slightly acid soils in full sun. Usually grown from semi-ripe tip cuttings, which may be taken throughout the year.

Phyllocladus
C/E/-15/8 × 3 (1.8)

A Pacific genus with three New Zealand species: P. alpinus, P. glauca and P. trichomanoides. They are commonly known as celery pines because the cladodes (phylloclades) are crowded at the tip of the branches, much like the leaves at the top of a celery stalk. Alternatively they are known by the Maori name: toa toa. They have stiff branches with terminal clusters whorls of cladodes that somewhat resemble oak leaves. P. alpinus and P. trichomanoides have light olive green foliage, while the new foliage of P. glauca is a stunning bluish-green, which turns to olive as the foliage matures. P. alpinus and P. glaucus are monoecious but P. trichomanoides is dioecious. Plant in moist well-drained soil. Celery pines are usually raised from seed sown at 18°C but will grow from semi-ripe autumn tip cuttings.

Picea
C/E/-25/10 × 4 (2)

Spruce is a genus of about 30 species of trees and shrubs. The spruce is the model for the traditional Christmas tree: upright and pyramidal with symmetrical horizontal branches clothed in short needles arranged radially along the branches. The commonly grown P. abies, P. glauca and P. pungens match the image on the card quite closely, but there are many hybrids and cultivated forms. These range from minute rockery dwarfs to 30 m high trees. The best known tree-sized Picea cultivars are the blue forms of P. pungens, the best know of which is ‘Kosteri’. It is a beautiful steel blue and perfectly symmetrical when grown well, although few perfect specimens exist and most eventually suffer some damage that spoils the shape. Spruces prefer cool moist well-drained soil with ample summer moisture. The species may be raised from stratified seed sown at 18°C, but the selected forms must be propagated vegetatively. Most are grown from semi-ripe summer and autumn cuttings, although the best forms of blue spruce are usually grafted.

Pinus  
C/E/-15/12 × 5 (3)

Perhaps because they are suchcommon timber trees, few pines are considered for their ornamental merit. Nevertheless, greater use could be made of these trees, especially the smaller species.

Pines vary widely in the size and arrangement of their needles and the size of their cones. Some, such as P. coulteri, have large cones while those of others, such as P. mugo, are quite insignificant. Pines also vary in their growing requirements, some are very cold hardy and extremely drought tolerant but others are frost tender or demand regular moisture.

There are not many cultivated forms of Pinus except for the very small cultivars of P. mugo and a few glaucous and golden foliaged forms. The species most likely to be seen in domestic gardens is the Mexican weeping pine (P. patula). It has very long drooping needles that are bright grass green when young. It is only hardy to about -10°C making it one of the more frost tender pines. P. wallichiana has a similar appearance when young and is hardier. However, it will become a very large tree. The Italian stone pine (P. pinea) is an attractive round-headed tree that remains compact for many years.

Most pines will grow in any well-drained soil. Garden pines are generally grown from seed, which should be sown at about 18°C. Selected forms are either grown from semi-ripe autumn cuttings or grafted.

Plagianthus 
B/D/-15/8 × 5 (2.5)

The ribbonwood (P. betulinus), so called because of its tough stringy bark is one of the few native deciduous trees and the only species of its genus in general cultivation. It is ultimately a large tree, but remains bushy for many years. The foliage of young trees is small and round, while the foliage of adult trees is bronze green, lanceolate and about 60 mm long with serrated edges. The small creamy flowers appear from late spring and are carried in panicles about 200 mm long. Ribbonwood will grow in any moist well-drained soil. It is usually raised from seed sown at 18°C or by semi-ripe autumn cuttings.

Plane Tree–see Platanus

Platanus
B/D/-25/15 × 12 (2.5)

The London plane tree (P. × acerifolia [hybrida]) is often seen in large parks, especially those in cities as it is very tolerant of air pollution. It is not considered to be a natural species but a hybrid between P. orientalis and the American sycamore (P. occidentalis). Although the London plant is far more widely grown, the Arizona sycamore (P. wrightii) is often considered to be superior because of its neat shape and bright white bark. All are large deciduous trees with 3-5 lobed, roughly maple-shaped, palmate leaves that may be up to 250 mm across. All species have peeling bark that often develops interesting patterns that are attractive in the winter when the trees are devoid of leaves. They are easily grown in any well-drained soil and may be propagated by stratified seed sown at 18°C or by open-ground winter hardwood cuttings.

Podocarpus
C/E/-15/15 × 8 (1.8)

The totara (P. totara) is one of the few native conifers to be widely grown in domestic gardens. At over 20 m high and very solidly built, the species is far too large for anything but parks and reserves. However, the golden foliaged form, ‘Aurea’, is smaller and very slow growing. It has small needle-like bright golden-yellow leaves and deeply fissured reddish-brown bark. P. hallii is similar to P. totara  but tends to grow at higher altitudes in the wild and is slightly smaller. Other species, not necessarily native, are also cultivated. Of these, P. macrophyllus from China and Japan is the most distinctive. It has deep green 150 mm long strap-like leaves and grows slowly to about 9 m high. The form ‘Maki’ has the largest and best coloured foliage. Most species have conspicuous red berry-like fruit with a single seed. This often leads to them being confused with yews (Taxus), which have similar fruit. Podocarps prefer cool moist well-drained soil with ample humus. The species may be raised from seed sown at 20°C, but the selected forms are usually grown from semi-ripe summer and autumn tip cuttings or, very rarely, grafted.

Populus
B/D/-25/15 × 4 (3)

Poplars are generally too large for domestic gardens but they are a feature of shelter belts in country areas. The common columnar Lombardy poplar (P. nigra ‘Italica’) is the variety most widely grown. Its bright green leaves are somewhat heart shaped and turn a bright yellow before falling. The flowers and fruit are insignificant. The other common species, white Poplar (P. alba) is something of a weed unless grafted onto non-suckering stock. Its leaves are palmate with 3-5 broad lobes, deep green above and silvery white below. It can be a useful foliage accent but often self-sows to the extent of becoming invasive. It really has too many bad points to be recommended, so it might be better to opt for P. canescens, which is similar but less aggressive. However, it is not as widely available. Poplars are easily grown in most soils but the poplar rust fungus can be a serious problem with some species. Species and non-suckering forms are generally raised from open ground winter hardwood cuttings, while selected suckering forms are usually grafted onto P. yunnanensis stocks. All poplars have strong aggressive roots so don’t plant them where they might cause damage to paths, drives, sewerage or other pipes.

Port wine magnolia–see Michaelia

Prunus 
B/D/-15/8 × 6 (2.5)

The ornamental Prunus — cherries, apricots, plums, peaches and almonds – are among the most common ornamental deciduous trees. Several species and many hybrids are grown and they range in size from the very dwarf almonds, such as the P. glandulosa forms, which are suitable for small gardens and containers, through to large spreading trees, such as P. sargentii, which may grow to 18 m x 12 m.

Always heavy flowering they vary in colour, size, style and season and growth habit. Among the most popular are the weeping and horizontal standards. These are naturally low, spreading plants that have been grafted onto upright standards from 1-2.5 m high. The standard trunk doesn’t grow any higher than the point at which it is grafted but the branches arch up and spread out to make a substantial plant.

Flower colours are mainly white and various shades of pink. There are also a few very deep pink, bordering on red, cultivars and some with orange tints. Flowers may be single, semi-double or fully double. Often a double-flowered form will also carry some single flowers. Many of the ornamental forms are sterile and do not bear fruit, but some develop small, usually inedible, fruit after flowering. The trees are generally very frost hardy, but some of the very early flowering forms, such as P. subhirtella ‘Autumnalis’ may suffer flower or bud damage from hard frosts.

This genus is easily grown although subject to several pests and diseases, the worst of which is silver leaf, a disease that seriously debilitates plants and may eventually kill them. See the section on fruit trees for details on the identification and control of Prunus pests and diseases.

Plant in moist well-drained soil. As most plants are hybrids or selected forms they are generally budded or grafted. The species may be raised from stratified seed sown at 18°C.

Pukanui (Puka)–see Meryta

Puriri–see Vitex

Pyrus 
B/D/-20/6 × 4 (2.5)

Pears are seldom grown as ornamentals but one non-fruiting species, the weeping silver pear’ (P. salicifolia ‘Pendula’) and one inedible species (P. calleryana) are grown for the beauty of their foliage. The silver pear is an upright tree that grows to 8 m but the weeping foliaged form ‘Pendula’ is grafted on a standard stem or trained to produce a small weeping tree. It has 75-100mm long, narrow, willow-like leaves that are covered in soft silvery hairs. In spring small white flowers appear.

P. calleryana also has white flowers, usually very early in spring. They are followed by small inedible fruits. This tree, which grows to about 9 m x 5 m, is grown for its autumn foliage display. It has 75 mm long glossy dark oval leaves with wavy edges. In autumn the foliage develops fiery orange and red tones. Both species are easily grown in well-drained soils, but they are inclined to be wind damaged when young and are best staked. The species may be raised from stratified seed sown at 18°C but ‘Pendula’ and other selected forms must be propagated vegetatively, usually by grafting. Specialist seed suppliers offer other species, such as P. ussuriensis, which also colours well in autumn and has small yellow inedible fruit.

Quercus
B/E or D/-15/20 × 10 (2.5)

The oaks are a large genus of about 500 species of evergreen and deciduous trees spread over much of the temperate Northern Hemisphere. The cork oak (Q. suber) is an evergreen species that is the source of cork and thus a valuable commercial tree but most of the others are grown as ornamentals. The common English oak (Q. robur) is a large deciduous tree with dark green deeply lobed 100mm-long leaves that tend to stay on the tree after they brown off in autumn. It usually sets large crops of rounded acorns. Scarlet oak (Q. coccinea) is another large deciduous species. It is widely planted for its vivid red autumn foliage colour. Many other deciduous species are grown but few of the potentially very useful American evergreen species are readily available. Specialist suppliers sometimes stock seed of the canyon live oak (Q. chrysolepsis) and the holly leafed Q. wislizenii, which are well worth trying. Most species are hardy to at least -15°C, often lower. They are generally easily grown in any well-drained soil and usually raised from  stratified seed (acorns) sown at around 20°C.

Queensland umbrella tree–see Schefflera

Redwood–see Sequoiadendron

Rhus
B/D/-25/8 × 8 (2.5)

Sumach or wax tree (R. succedeana) has some of the most vividly coloured autumn foliage of any deciduous tree. It is often seen as a large multi-trunked shrub but it is best trained to one or two main stems by pruning to shape when young. The leaves are pinnate, about 40-50cm long, and composed of 15-30 leaflets. The new spring growth is covered with a fine hair that can cause a contact dermatitis. In summer the leaves are deep green but in the autumn they change to orange then intense red and purplish crimson shades. The small spring flowers develop into large reddish cone shaped seed heads that are very waxy. They can supposedly be used as candles simply by threading a wick through them. The plant suckers very freely and can become invasive so it is difficult to remove once established. R. typhina is a very similar species. Both are easily grown in any moist well-drained soil. Plant in full sun to get the best autumn foliage colours. Usually grown from root cuttings or suckers but may be raised from stratified seed sown at 18°C. Specialist suppliers often stock seed of less common species, such as the evergreen and drought tolerant R. lancea.

Rimu–see Dacrydium

Ribbonwood–see Hoheria and Plagianthus

Robinia
B/D/-25/10 × 6 (2.5)

R. pseudoacacia ‘Frisia’ is the most commonly planted member of this genus and has become enormously popular over the last ten years. It has bright golden-yellow 200 mm long pinnate leaves composed of about 14 rounded leaflets. The white flower clusters are not insignificant but are seldom seen on this form. In common with most Robinia species it has vicious thorns that are seldom seen until you have to extract them from your flesh. The green-leafed true species of R. pseudoacacia has regular early summer crops of clusters of fragrant white flowers that are followed by bean-like seed pods. A selected form of another species, R. hispida, has recently been promoted as the ‘Pink Wisteria Tree’. It has long racemes of pink flowers and grows to about 4m. Many interesting small forms of Robinia, such as ‘Mop Top’ and ‘Lace Lady’ are now widely grown. They make excellent tub specimens. All are easily grown in well-drained soil but have brittle branches that are easily wind damaged, so stake them well when young. The species may be raised from stratified and soaked seed sown at 18°C; selected forms and hybrids are usually budded or grafted.

Rowan–see Sorbus

Rubber tree–see Ficus

Salix
B/D/-25/10 × 8 (3)

Willows are very attractive but they need room to grow. This genus includes about 300 species of trees and shrubs, the most widely cultivated of which is S. matsudana, commonly seen used as a quick growing shelter belt. The shelter forms are not grown as ornamentals but the tortured or corkscrew willow (S. matsudana ‘Tortuosa’) is an interesting cultivar. It has twisted and contorted branches that are, of course, most obvious in the winter when the tree is leafless. The weeping willow (S. babylonica) is a feature of many parks and gardens. It is a graceful tree with long weeping branches covered in bright green foliage, but has high water demands and a strong fibrous root system. The common pussy willow (S. caprea) is generally seen growing wild along riverbanks. Its fluffy catkins are attractive in early spring but its untidy growth and invasive habits rule it out for all but the largest gardens.

The tree sized willows will all grow to at least 8m but there are some small species. S. purpurea is the best known of these. In its darkest forms the catkins are an intense reddish purple. The leaves are glaucous, often with a hint of purple on the reverse. It grows to about 5m x 3m. Willows will grow in any soil that never entirely dries out. They are usually raised from open-ground winter hardwood cuttings.

Schefflera
B/E/-3/7 × 4 (2.5)

There are two common species: Queensland umbrella tree (S. actinophylla) is often grown as a house plant, while the other, the New Zealand native S. digitata, is often seen in the wild. Both species have deep green digitate leaves composed of around 5-12 leaflets. The leaves of S. actinophylla are up to very large with leaflets up to 300mm long. The leaflets of S. digitata rarely exceed 200mm long and are dull dark green as opposed to the glossy bronze green of S. actinophylla. Neither is very hardy but S. digitata will withstand -3°C once established. S. actinophylla is unlikely to survive -2°C without damage. The greenish yellow turning to red flowers appear in spring. They are not particularly attractive but are carried in large conspicuous panicles. The flowers are followed by reddish brown berries. Best in moist humus-enriched soil in sun of light shade. Propagate by seed sown at 20°C or by semi-ripe cuttings, which may be taken whenever the new growth is reasonably firm.

Schinus
B/E/-6/10 × 8 (2.5)

Two species of this 15 species genus are commonly cultivated. Both are South American natives and both are known as the pepper tree. S. ariera (molle) is a graceful, weeping, spreading tree from Peru. It has bright green finely divided pinnate leaves and very deeply fissured corky bark. The drooping panicles of tiny cream flowers that appear in summer are not a major feature but they are followed by small green berries that redden as they ripen. These add interest to the tree in winter. Easily grown, it may even be slightly invasive in some areas. S. terebinthifolia is a Brazilian species commonly called the Brazilian pepper tree. It has larger bronze green leaves composed of fewer leaflets than S. ariera. Its fruit is also slightly larger but at 8 m × 6 it is ultimately a smaller tree. Both species are reasonably hardy if protected from frost when young. These trees tolerate most soils but require good drainage. They may be raised from seed sown at 22°C or by semi-ripe summer and autumn cuttings.

Sequoiadendron
C/E/-20/20 × 10 (2.5)

The giant sequoia or big tree (S. giganteum) is usually regarded as the world’s largest tree. It may grow to 115 m high with a trunk up to 10 m diameter. It is a very straight conical tree with deep green slightly prickly cupressoid foliage. It has a stoutly buttressed trunk with deeply fissured reddish brown bark. Obviously, it is far too large for most gardens, but there is a very slow growing narrow form called ‘Pendulum’, which has weeping branches and is useful for adding height with very little width. This is an interesting specimen but it requires careful staking and training to do well. It prefers to grow in cool moist well-drained soil, although it is drought tolerant when established. As a selected form ‘ Pendulum’ must be propagated from semi-ripe cuttings taken in late summer or autumn.

Silk tree–see Albizia

Silver birch–see Betula

Silver pear–see Pyrus

Sophora 
B/E or D/-10/8 × 5 (2.5)

A widespread genus of evergreen and deciduous trees and shrubs.

S. japonica is the most widely grown species. It is a deciduous species with 200 mm long light green pinnate leaves and cream, or occasionally pale pink, flowers in 200–300 mm long terminal panicles. It may grow to 15 m x 12 m but is often grafted onto 2 m standards to produce a small weeping tree. It is hardy to at least -25°C. S. secundiflora is a rare North American species with fragrant lavender blue flowers. It is evergreen, hardy to -6°C and grows to 8 m high.

Sorbus 
B/D/-25/8 × 3.5 (2.5)

The bright orange berries of the mountain ash or rowan (S. aucuparia) are a common sight in autumn and make it the most widely recognised member of this Northern hemisphere genus. Most species have pinnate leaves and terminal clusters of small creamy white flowers in spring. The flowers, which are often rather unpleasantly scented, are followed by showy berries. The colour of the berries varies with the species. Mountain ash has orange berries, S. americana has white berries, while those of S. hupehensis are white tinted pink. The smaller growing (up to 4m x 1.8m) S. vilmorinii is available in pink, yellow or red berried forms. Some species, most notably S. discolor, have attractive autumn foliage but most show little autumn colouration. Rowans are easily grow in any well-drained soil and are most at home in areas with distinct winters. The species may be raised from stratified seed sown at 15°C but the selected forms are usually layered or grafted.

Southern beech–see Nothofagus

Spruce–see Picea

Sterculia–see Brachychiton

Strawberry tree–see Arbutus

Styrax
B/D/-20/7 × 4 (2)

These small deciduous trees have a neat growth habit and an attractive spring flower display. The most common species, S. japonica, grows to about 7m and has deep green pointed heart shaped leaves and slightly drooping racemes of small bell-shaped white flowers. S. obassia is a similar but taller species (10m) that has fragrant flowers. Both prefer cool, moist, well-drained soil and cool, moist summer conditions. They blend well with rhododendrons, camellias and fuchsias. Usually raised from stratified seed sown at 18°C but may also be grown from winter hardwood cuttings and late summer or autumn semi-ripe cuttings.

Sumach–see Rhus

Swamp cypress–see Taxodium

Sweet gum–see Liquidambar

Tamarix  
B/D/-20/6 × 3 (2.5)

This genus includes about 80 species of shrubs and trees, most of which are deciduous. Many are untidy rangy growers, but among the others are some of the best flowering trees for coastal conditions. They have tiny adpressed leaves that are reminiscent of heather (Calluna)and which are carried on slender branches and wiry twigs. T. aphylla has silvery grey leaves and is primarily grown as a foliage plant. In late spring and early summer, depending on the species, plumes of minute pink flowers develop at the ends of the branches. T. chinensis is usually regarded as the best flowering species. Tamarisks prefer light well-drained soil in full sun. They are able to tolerate the full blast of coastal salt winds but are neater and heavier flowering if cared for with regular water and occasional trimming. They may be raised from seed sown at 18°C but are usually propagated by open-ground winter hardwood cuttings.

Tawa–see Beilschmiedia

Taxodium
C/D/-25/15 × 6 (3)

The swamp cypress (T. distichum) is the best known species of this ancient genus of deciduous conifers. It is an attractive large tree that is well known for its ability to grow in as much as 80 cm of water. It develops special breathing roots that emerge from the water’s surface some distance from the main trunk. These ‘knees’ are a prominent feature. However, the tree is mainly grown for its graceful light structure, rugged bark and beautiful rusty red autumn foliage colour. The fine pinnate leaves develop the colour quite early yet remain on the tree until early winter. Swamp cypress will grow in moist garden soil and, of course, it is not fussy about drainage. It is usually raised from stratified seed sown at 22°C.

Taxus
C/E/-30/12 × 10 (2.5)

The yew (T. baccata) has been cultivated for over 1000 years, during which time it has mainly been used for hedging and topiary. The species is very large shrub or multi-trunked tree with a dense covering of blackish-green, slightly glossy, leathery 25 mm long needle-like leaves. In spring the strobili are quite apparent. These are followed by bright red berry-like fruits that contains one seed.

Not surprisingly for a tree that has been in cultivation for so long there are many cultivated forms. The best known is the columnar ‘Fastigiata’. This is often used for flanking entrances or driveways or for making narrow hedges. All forms of T. baccata will withstand severe trimming and are excellent hedging plants. Golden foliaged, variegated and dwarf cultivars are also quite widely grown. Other species are seen occasionally, but T. baccata is by far the most common.

Yews prefer moist well-drained soil and a position in full sun. The species may be raised from stratified seed sown at 18°C, but the cultivars are usually grown from semi-ripe summer and autumn tip cuttings.

Thuja
C/E/-30/8 × 4 (2.5)

Because it commonly planted as farm shelter T. plicata is probably the most widely grown of this genus. However, none of the true species are much used in domestic gardens. Most garden forms are cultivars of T. occidentalis or T. plicata. Both of these species have small scale-like leaves and fan-shaped foliage sprays with small spherical cones that are very resinous. The garden forms are usually rockery dwarfs or shrubs. The best known of the larger hybrids is the variegated T. plicata ‘Zebrina’, which grows to about 2.5 m x 1.5 m. Thujas are very hardy and will grow in any well-drained soil. The species may be raised from stratified seed sown at 18°C; the cultivars forms are usually propagated by summer and autumn semi-ripe cuttings.

Tilia
B/D/-25/15 × 10 (2.5)

The lime or linden (T. europaeus) is a large tree that is widely used for avenue planting. The leaves are about 75–100 mm long, light to mid green, heart-shaped and deeply veined with a prominent point. They develop golden yellow to orange tones in autumn. The small cream flowers, which appear in late spring, are scented and very attractive to bees. They are followed by clusters of small brown seed capsules. The linden is easily grown in any moist well-drained soil, although it is too large for small gardens. The species is usually raised from stratified seed sown at 18°C, while the selected forms grafted. Other species, such as the smaller leafed T. cordata and the upright growing American linden (T. americana) are seldom sold in garden centres. However, seed of these and other species is available from specialist seed suppliers.

Titoki–see Alectryon

Totara–see Podocarpus

Tree of Heaven–see Ailanthus

Tulip tree–see Liriodendron

Tupelo–see Nyssa

Ulmus
B/D/-30/15 × 10 (2.5)

The recent threat of Dutch elm disease has raised the question of whether it is worth the risk of planting these trees. There are many magnificent elms throughout the country but it may only be a matter of time before they go. Several species of these large trees are grown. Most species have 75-100 mm long deep green, deeply veined, rounded leaves with serrated edges. The most widely planted are U. glabra and U. procera and two cultivars dominate the local plantings, they are the golden elm (U. procera ‘Louis van Houtte’) and the wide-spreading weeping Camperdown elm (U. glabra ‘Camperdownii’). All of too large for small gardens, but they make magnificent specimens for large lawns or parks. Elms are primarily deciduous, however, the evergreen U. parvifolia may occasionally be seen. It has smaller leaves (60 mm long) and interesting peeling bark rather like the London plane. It is less hardy, tolerating only about -8°C until well-established. All species have early spring flowers with conspicuous bracts but they are rarely considered a feature. The papery seeds can make a mess and elms are notorious for suckering but they are impressive stately trees. They are easily grown in any moist well-drained soil The species may be raised from stratified seed  sown at 18°C; the selected forms are usually grafted.

Vanilla Tree–see Azara

Virgilia 
B/E/-6/10 × 8 (4)

Although they provide a good display of spring and early summer flowers care should be taken when planting these South African natives. In many areas they self sow freely and may become weeds. The two species, V. capensis and V. divaricata are considered by some authorities variations of the same species. V. capensis is slightly larger growing with lighter coloured flowers, but there is not much to choose between them. Both have deep green, somewhat leathery, pinnate leaves composed of many small leaflets. The underside of the leaves is light green to slightly silvery. From spring to early summer pendulous clusters of pink to mauve sweet pea-like flowers appear. A tree in full flower is quite spectacular but the display doesn’t last long. Virgilias are easily grown in any light well-drained soil. They are often best used as quick-growing temporary shelter as trees over fifteen years old often become very untidy and open. They are usually grown from seed, which should be soaked and sown at 18°C.

Vitex
B/E/-4/15 × 10 (2.5)

The puriri (V. lucens) is one of the few New Zealand native trees with pinkish-red flowers. The flowers, which are carried in panicles, are most often seen in late winter, although they may occur at any time. The flowers are followed by bright red 20 mm-long berries. The foliage of the puriri is very handsome: the leaves are a lustrous, glossy green; digitate and composed of 3–5 broad leathery leaflets that are up to 125 mm long. Puriri is a very impressive tree in all respects and, fittingly, it is host to one of our most impressive insects: the puriri moth. The caterpillars of this large moth can often be found on trees in the wild, but they do little damage. Puriri does best in a humus-enriched, moist well-drained soil and should be shaded and protected from wind and frost when young. It is usually raised from seed sown at 20°C, but may also be propagated by semi-ripe cuttings whenever these are available.

Wattle–see Acacia

Weinmannia
B/E/-15/15 × 6 (2.5)

Kamahi (W. racemosa) is a very attractive New Zealand flowering tree that could be far more widely grown in gardens. It has elliptical deep bronze-green, serrated-edged leaves that can be up to 100mm long, although they are more commonly around 75 mm. Young trees have leaves composed of 3 leaflets, but in adult trees the leaves are single bladed. In summer, the tree produces masses of 150 mm-long, narrow creamy-white bottlebrush-like flower heads. The massed flowers often swarm with bees as they are heavy with nectar and pollen. The flowers are followed by 20 mm diameter red berry-like fruits. There is a purple leafed form that is occasionally available. Kamahi prefers a moist, slightly acid soil and is easily grown where frosts are not severe. It can be propagated by seed sown at 18°C or by semi-ripe summer and autumn cuttings. The towai (W. silvicola) is a similar species that occurs in the north of the North Island, although it appears to be hardy well outside its natural range.

Wellingtonia–see Sequoiadendron

Willow–see Salix

Willow myrtle–see Agonis

Whau–see Entelea

Yew–see Taxus

Copyright Geoff Bryant