Leaves vary tremendously between species. Large, flat leaves capture the maximum amount of light. Narrow pine needles are adapted to be drought resistant. They don’t get weighed down with heavy layers of snow, but have a large surface area in comparison with their volume. This way they are still able to capture plenty of light. Some species have waxy leaves in an attempt to prevent excessive evaporation, while others have leaves covered in dense hairs, which achieve the same end. All leaves have one thing in common: they emerge from buds which form at the tips of shoots (apical buds), often in clusters. On conifers, buds also form at random points along each shoot, of which the precise number and density depends upon the length of the shoot and the vigour of the tree. On broadleaved trees, a bud appears at the base of each leaf stalk (petiole). These buds are called axillary buds.
When pruning or pinching growing shoots on a bonsai, it’s important to consider the location of such buds because these are the points from which new shoots will emerge. If the bud faces left, then the shoot will grow to the left; if it faces right, the shoot will bear right.
Brightly coloured Trident Maple (Acer buergeranium) leaves in autumn. Chlorophyll is always green but its colour has been overwhelmed by red pigmentation.
The buds of three types of tree: (1) opening maple buds, (2) the buds of an elm, just opening and (3) pine candles extending as they mature.
Buds
Buds are miraculous things. Their outer scales are modified leaves whose function is to protect the delicate contents. Inside each mature bud is a tightly packed shoot, complete with its first few leaves, the apical bud and even embryonic axillary buds.
A bud looks just like the inside of a cabbage, if it were cut in half vertically. Imagine the intricacy of an elm bud with all those elements packed into something the size of a pinhead. Buds vary in character as much as leaves do. In the winter months, buds provide a reliable means of identifying deciduous trees even without any leaves to go by.
New shoots also vary. Pines, for example, produce vertical shoots, known as candles, which extend rapidly with their tiny needles pressed flat against them. Once they have reached their fullest extent, the needles begin to elongate and peel away from the shoot. Spruce and larch buds open to reveal tufts of tightly packed, soft needles, which look for all the world like miniature shaving brushes.
During the summer months, leaves make sugars, and when eventually they become redundant, they turn brown and fall. In the case of deciduous trees, by their first autumn, the leaves are worn out, whereas the needles (or leaves) of conifers often last for two years, or even longer.
The joint between the petiole (leaf stalk) and the shoot seals off in deciduous trees, and the chlorophyll breaks down, allowing the residual pigments to show.
A cabbage is a perfect illustration of a giant bud which contains a partially developed central shoot, tightly packed leaves and even embryonic axillary buds.
This is what causes that brilliant blaze of autumn colour that people who live in temperate zones are privileged to enjoy. Spectacular autumn colour cannot always be relied upon. It will depend upon the health and vigour of the individual trees, and the feeding programme that was followed in the preceding summer.
Weather also plays a part: in wet years the autumn colours are poor. However, when the autumn is clear with sunny days and frosty nights, colours produced will be intense.
While nothing can be done about the weather, it is possible to enhance the chance of your achieving a show of the best possible colour by maintaining control over the feeding and watering of your plants.
THE ART OF BONSAI
Bonsai aesthetics
There is something about a tree that touches one’s very soul. This feeling probably dates back to primeval days when early humans relied upon trees for protection, warmth shelter and food. Where trees were found, there was a potential home. Throughout history, trees have played a major role in primitive religions and mystical powers have been attributed to them. This strong emotional tie still resides within all of us, and the pleasure that is to be gained from creating and keeping a miniature tree of one’s own appeals to a great many people.
The simplified image of a group of bonsai trees echoes the appearance of the copse of full-sized trees depicted opposite. In the spirit of the Group Planting Style, the grower has aimed for an effect that looks entirely natural.
In spite of all the horticultural knowledge and practical techniques you may master, bonsai is a visual discipline. It is all about forming an idealized, miniature image of a tree in an imagined natural setting. This could be a graceful lowland maple standing proudly in an open meadow, a forest of elms on a distant hill; or an ancient pine, torn and battered by mountain storms. The possibilities are endless, the horizons limited only by the scope of your own imagination. Nowadays, some artists go way beyond the accepted image of the tree and create abstract, living sculptures, with a mass of swirling deadwood interlaced with foliage. But, to those brave souls prepared to take the imaginative leap, these may be seen as credible arboreal forms.
A bonsai, of necessity, has to be an over-simplified image. A fully-grown pine tree could have around 50 branches, but on a bonsai there is obviously not enough room. Leaves or needles will be reduced in size, though they are never so small as to be in perfect proportion to the tree. In order to accommodate such subtle simplification, bonsai has its own set of aesthetic ‘rules’. These have only been developed as guides to design, they are not meant to be rigidly followed at the expense of your own artistic sense.
Proportion
In a full-sized tree the relation between the thickness of the trunk and the tree’s height could be 1:30 or 1:40, perhaps more. However, in a bonsai these proportions would make the trunk appear unbelievably feeble. A proportion of 1:10 is the maximum allowable in most cases. Nowadays, the trend is toward an even tighter proportion of 1:4, or even less. A heavy trunk not only carries the implication of great age but permits the formation of interestingly textured, mature bark.
The proportional relationship between the space below the lowest branch and the total height of the tree is also important. The lowest branch should be between a quarter and one-third of the total height. A notable exception to this principle is the Literati Style, which depicts a lone conifer on a mountainside, battling on bravely after all its neighbours have succumbed to the elements.
The proportion of the foliage will always be subject to compromise, because, although it will become smaller with trimming, it will always seem oversized. A heavy trunk will appear to balance the foliage, but choice of species is the key. Types with naturally large leaves should either be avoided or grown as larger bonsai. Only species with tiny leaves can be grown as small bonsai. The miniature bonsai, mame (miniature) or shohin (small), small enough to fit in the palm of your hand, are created from species with small leaves. In cases where larger-leaved species are used, a leaf stalk represents a branch and a leaf, a mass of foliage.