The maples provide us with a wide range of mostly hardy deciduous and easily cultivated trees. Many are notable for their elegance and for the spectacular effect of their autumn foliage. The treelike forms of Acer japonicum and A. palmatum are particularly significant in this respect. Garden forms of sycamore (A. pseudoplatanus), Norway maple (A. platanoides) and the box maple (A. negundo) can be useful for screening and for garden effect, while several other species are grown as much for their unusual bark effects as for the autumn colour of their leaves.
Acer campestre, the common, field or hedge maple, is often grown and clipped as a hedge plant but this hardy European species if unpruned will make a picturesque, round-headed, small or medium-sized tree. It is notable for the clear, bright yellow in autumn of its attractively lobed leaves and will show up well as a hedgerow tree or as a specimen near the perimeter of a larger garden. There is also a variety schwerinii with leaves which are purple tinted in the spring.
A. cappadocicum is a medium to large-sized hardy tree from the Caucasus, having large five or seven-lobed leaves which colour well in the autumn. It is usually represented in cultivation by its garden varieties which are both vigorous, fast-growing trees as useful for screening as for foliage effect in the garden. In the variety aureum the young leaves unfold. Red tinted, turn golden yellow for several weeks, then change to green, finally reverting to yellow again in the autumn. In rubrum the leaves of the new shoots on young trees are blood red, while on older trees the unfolding leaves are deep purple red. Striking and unusual effects are created by associating these two varieties together.
The snake-bark maple, A. davidii, is a small Chinese tree of open spreading habit. This is one of the group of maples notable for the attractive, white, snakeskin-like striations on the bark of the trunk and branches. The leaves colour a rich red in the autumn when the winged fruits or ‘keys’, also suffused red, hang thick clustered along the branches. The form usually available is called George Forrest (syn. Horizontalis), in honour of the great plant collector who introduced it to western gardens in 1922. There are several allied species exhibiting similar snake-bark qualities as well as autumn colour of leaf. Among these are A. capilhpes; A. grosseri; A. hersii; A. pensylvanicum, and A. rufinerve. All make attractive small or medium-sized garden trees and are of Asiatic origin with the exception of the North American A. pensylvanicum.
The choice Chinese species A. griseum, the paperbark maple, is generally regarded as one of the most striking and beautiful of all garden trees. The peeling from the trunk and main branches of its mahogany-brown outer bark to reveal orange or cinnamon-coloured underbark is its most outstanding feature. Delightful soft red and orange autumn colouring of leaf, unfailingly produced, is a further attribute. An ideal specimen tree for the small garden, it usually assumes a neat vase or wine-glass shape in outline, slowly attaining 10 or 12 ft. in about fifteen years. Acer griseum grows well on most soils including chalky ones; it may make as much as 45 ft. on rich loamy soils.
A. japonicum is one of the group known as the Japanese maples. It is a slow-growing, small, bushy-headed tree, usually represented in cultivation by the following varieties. Aureum is a choice, rather slow-growing but very beautiful form effective throughout the growing season by reason of its handsome soft yellow leaves. For the best effect plant in a sheltered, semi-shaded position preferably facing west in order that the late afternoon sunlight is projected most tellingly through the yellow leaves. Care in siting is important as the leaves will scorch in full sunshine. With leaves up to 6 in. across, vitifolium is the largest-leaved Japanese maple and one which contributes a vivid kaleidoscope of colour to the autumn scene. Yellow, orange, scarlet, crimspn, purple and green are usually represented particularly on neutral or acid soils. It is a more vigorous small tree than aureum and often as wide as it is high.
The box elder, A. negundo, a North American maple, is usually seen in cultivation as a medium-sized tree with a widespreading head. The bright green young shoots are a notable feature; the pinnate leaves have a variable number of leaflets, bright green with paler undersides. A useful screening tree, the box elder, requires plenty of room if allowed to develop its full spread and is perhaps better represented in small gardens by its several variegated forms which are generally more modest in ultimate growth and more striking in garden effect. Auratum is one of the few garden trees retaining its bright golden-yellow leaves throughout the growing season. It is a striking small tree. Elegans (elegantissimum) is a form with its leaves broadly margined bright yellow. Variegatum (argenteovariegatum) is the most commonly planted variety and is most effective with its leaves irregularly bordered with white, some leaflets may be completely white. These three varieties are very worthy garden trees but have a tendency to produce branches where the leaves have reverted to the more vigorous green of A. negundo. Such branches should be carefully pruned out as soon as they are noticed; if neglected they will tend to dominate, eventually suppressing the variegated form.
A. nikoense, the Nikko maple, a small to medium-sized, round-headed tree from Japan and central China, is related to A. griseum. The large leaves, consisting of 3 to 5-in, long leaflets with grey undersides, colour magnificently a combination of scarlet, flame and yellow unfailingly each autumn. Suitable for all soils, this is one of the most beautiful, hardy, autumn-colouring trees that we can grow.
In cultivation A. palmatum, the Japanese maple, is seen as a small round-headed tree, up to 20 ft. high and as much through. The five or seven-lobed bright green leaves assume rich autumn tints of red, orange and yellow. This and the more robust of its many forms will grow in a moist but reasonably well-drained situation on most soils including alkaline or chalky ones. A sheltered semi-shaded site tree; the young foliage is tinted with yellow on the upper surfaces and with purple beneath. Nizetii and Simon-Louis Freres are similar, often with pink tinting in their leaves.