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Tree Basics

Few plants provide as much pleasure, or make such a useful contribution to the immediate environment, as the trees you plant in your garden.

Few plants provide as much pleasure, or make such a useful contribution to the immediate environment, as the trees you plant in your garden.

Trees are the most important plants in any landscape and in a garden their role is even more significant. They play a dominant part in a physical and aesthetic sense and also because man has a spiritual affinity with trees such as he has with no other plants — not even those on which he relies for his daily bread.

Standing at the foot of a giant yellowwood or an ancient baobab, olive or cedar, one is overcome by a feeling of awe. It is not merely the size which impresses, it is also the spiritual quality which an old tree infuses into its surroundings and the fact that, during the generations when it was growing to maturity, different civilizations rose and fell. On looking at old trees one is not surprised that through the ages some of them have acquired legendary attributes and been regarded as sacred, either individually or in groves.

Trees give an air of maturity and per­manence to a garden. They add height and depth to even simple garden de­signs, and provide shelter and privacy. Deciduous trees give shade in summer, while in winter the naked branches have a stark beauty outlined against the sky.

Evergreen trees are attractive throughout the year, and are especially appreciated in the drab months when there is little colour in the garden.

Trees that are carefully chosen and planted can create an aura of tran­quillity in public or private gardens. Their value can easily be appreciated in urban areas where they help break up the occasionally stark geometric out­lines of large buildings. An area that presents an unbroken vista of red‑tiled roofs can change its appearance completely with the ad­dition of properly sited garden and street trees.

Like other plants, trees condition the air by taking in carbon dioxide and giving off oxygen. Trees also have a definite cooling effect on their im­mediate environment. During warm weather, considerable hot air is generated above driveways, concrete paths and paved barbecue areas. Suitable shade trees can help to counteract this summer heat.

Most people select ornamental trees for their foliage, flowers and forms, or for a specific purpose, such as to pro­vide a windbreak. As trees have to be lived with for many years, it is vitally important from the beginning to choose the right tree for the right purpose or place. Even in a small sub­urban garden, a tree must be in keep­ing with the surrounding area. This does not mean that your choice is severely restricted, but if your neigh­bour has a Cinnamomum camphora (Camphor tree), one such tree is probably enough in the immediate area.

While you do not have to follow the local pattern slavishly, it is unwise to ‘fight’ the environment with the most unusual or impressive tree you can possibly find. Study the setting to see which tree will be the most suitable. In some situations an exotic tree may look out of place, and vice versa.

Inexperienced gardeners often make the mistake of purchasing a well‑pre­sented young sapling from a nursery without considering the ultimate size and shape of the tree. Always ensure that the tree is suitable for the position it will occupy before you buy. Trees come in a wide variety of shapes and sizes. There are trees with coloured or variegated foliage; tall, nar­row varieties; trees that are pyramid­shaped or round‑headed, and trees with foliage that casts only light or dappled shade.

There are tall, spreading trees, suit­able for country homesteads or large, formal gardens; there are medium‑sized trees for ordinary suburban gardens, and small trees suitable for townhouses or the courtyards of inner city areas.

Choose trees that suit the size of your garden in order to maintain a sense of proportion. In a large garden, a tree such as a tall‑growing Schinus molle (Pepper tree) may be very attractive, but in a small court­yard garden it would be completely out of place.

Even in small gardens where none of the chosen trees will exceed 7m in height, you can screen out the roofs of neighbouring houses, and, using a good choice of dense‑growing shrubs or climbers, you can screen out the side fences or walls as well. The choice becomes somewhat narrower when you have to choose plants for a par­ticular purpose.

A windbreak requires densely foli­aged evergreens to give the required protection; seaside gardens are usually suitable only for trees that can tolerate salt‑laden winds.

If you need shade use wide‑spreading trees like Schinus tere­binthifolius (Brazilian pepper) or Casu­arina cunninghamiana (River she‑oak).

If a tree is to be planted in the fore­ground, open shapes such as Betula pen­dula (Silver birch) or Syzygium corda­tum provide a frame for the rest of the garden.

For a boundary, the rounded, more solid shapes of Castanospermum australe (Black bean tree) or Acacia podalyriifolia (Pearl acacia), or the dense, pyramid shape of Cedrus deodara will give a feel­ing of privacy by obscuring the houses beyond.

Every garden is improved by at least one flowering tree. If you choose a tree which is also valued for its foliage, so much the better. Prunus laurocerasus (Cherry laurel) and Callisternon species (Bottlebrush) are examples of flowering trees suitable for small gardens.

For larger gardens you may choose from a variety of trees such as Bauhinia variegata (Jungle orchid tree) and Lag­unaria patersonii (Queensland pyramid tree).

Trees with foliage that colours in autumn bring a unique beauty to the garden, especially in cooler climates where the colours are often deeper and longer lasting. Acer palmatum (Japanese maple), Rhus succedanea (Wax tree) and Quer­cus palustris (Pin oak) all have striking foliage during autumn.

The amount of work to be done in the garden can be greatly reduced by adopting informal layouts for its or­namental part. Once planted, trees and shrubs require little attention. They make an ideal setting for annuals, per­ennials and bulbs, and in many cases provide both the light shade and the shelter in which many of these plants thrive.

If you intend to plant a single speci­men tree, on a lawn, at the back of a wide border, or near a boundary, con­sider carefully the merits and disadvan­tages of your choice. If you are choosing a tree for its shape, foliage, or for an outstanding feature such as weeping growth, coloured stems or long‑lasting, per­sistent berries, only the soil and pos­ition, and the eventual growth rate, need to be considered.

On the other hand, if you choose a tree for its flowers or autumn colours, try to ascertain its appearance at other times of the year.

Evergreen trees are popular not only for their screening value, but also for their beauty of shape. Once established, many evergreens, and especially certain conifers, are both wind‑resistant and drought‑resistant.

Choosing the planting sites In the average suburban garden, there is only sufficient space for half‑a‑dozen trees at most. In many cases there may only be room for two or three. Planning is therefore important; each tree must be planted in exactly the right position. If placed too close to the front boundary, the branches may spread over the footpath, obstructing passers‑by or interfering with overhead power lines.

Medium‑ to large‑growing trees should not be placed too close to the house. There is always the risk of danger to the foundations or sewerage or drainage pipes, and falling leaves — from evergreen as well as deciduous trees — can block down‑pipes and guttering.

In larger gardens, a group planting of two or three trees is more effective than a single specimen tree. The best effects generally come from letting one shape dominate the group — one tall, thin tree, one triangular‑ shaped fir and one bowl‑shaped tree will just look messy.

No set pattern can be given, but the trees should usually belong to the same genus and have roughly the same di­mensions and shape. Three different varieties of the same tree, with differ­ent coloured flowers or fruit, make a handsome group. So does a group with slightly differing leaf shapes and autumn tints.

The spacing of group planting varies. In the case of silver birches, the upper branches may be allowed to in­termingle, but the recommended spac­ing for most trees is about half the total spread of both trees.

The usual rules of spacing do not apply to windbreaks or screen plant­ings, where the idea is to achieve an effective barrier or to provide privacy. These plantings can be made as close as 1 m apart, particularly if smaller trees are used. The initial spacing can allow for the removal of every second tree as they grow larger.

Trees such as Cupressus macrocarpa (Monterey cypress), Myoporum laetum (Manatoka), Casuarina torulosa (Forest oak) and Cupressus leylandii make good windbreaks as well as being useful screening trees, especially around ponds and pools, where leaf drop needs to be minimised.

Popular trees are relatively inexpen­sive, but rare types may need a substan­tial outlay. In such a case, it is even more important to inspect a mature specimen of the tree of your choice in a nursery, park, or botanic garden. Take a look at it when it is at its best — either in flower, fruit, or autumn colour.

If you take enough trouble, you can plant a tree of almost any size, but once a tree is more than 4m or 5m tall the trouble involved increases, and the chances of success diminish.

You should rather buy a tree when it is small. This will give you the added pleasure of watching it grow through its most vigorous, formative time, allowing you to enjoy the foliage at eye level.

Finally, a word of caution:  Many indigenous trees are protected. Do not attempt to harvest saplings in the wild. Purchase your trees from trustworthy, registered nurseries. In addition, all gardeners should be aware of the listed noxious weeds and alien invader plants, which include many tree species such as weeping willow, white poplar, most of the wattles, Australian blackwood, many of the Pines and so on. If a friend offers you a sapling from his garden, do the right thing and check to ensure that you are not breaking the law by planting it. More information can be obtained by visiting

Visit the tree section of Gardening Made Easy   ( regularly. We will be adding a series of posts on Landscaping with Trees, Tree care, Gardening with Indigenous Trees, Flowering Trees and more.