Choosing Trees and Shrubs for Bonsai
In theory, it is possible to use any type of tree or shrub for bonsai, although some subjects are more suitable than others. The principal characteristics you should look out for, when selecting a plant, are an interesting trunk and good arrangement of branches, attractive bark color and texture, and compact and finely textured foliage (preferably with small leaves). If you want a subject with flowers or fruits, these must be small.
Many very beautiful trees, including the colorful maples, crab apples, and graceful larches are ideal. So too are evergreens with finely textured or needle-like foliage, such as cedars, pines, and junipers.
Large and Small Subjects
Many dwarf forms, such as the dwarf birch, Betula nana, adapt readily to bonsai, particularly as small-scale trees. A number of readily available and fast-growing garden shrubs, such as quince, cotoneaster, and pyracantha, are easily pruned to tree-like shapes. At the other end of the scale, there is the real challenge of trees like the English oak, Quercus robur, that in nature grow to huge proportions.
Some exceptions to the bonsai ideal of small leaves and fine twigs, such as the ornamental cherries, Prunus, provide wonderful seasonal effects with their lush flowers. However, if you have a restricted space that will accommodate only one or two bonsai, do not choose species that make a short-lived display in one season, and afterwards lack interest.
For year-round interest, you need not necessarily choose evergreen species, because deciduous trees such as elms and maples make a particularly impressive sight in the winter months, when their fine branch and twig structure is fully revealed.
Inspiration from Nature
Many people are attracted to bonsai through a love of nature. Even if you live far from open landscape, with bonsai you can enjoy the magnificence and beauty of nature recreated on a manageable scale, because the specimens have been inspired directly by the way in which trees grow in the wild.
Whatever you do in bonsai should reflect your observations of nature, related to the basic guidelines of bonsai cultivation. In nature, there is a wide variety, not only of different species, but also of different ways in which trees grow depending on their environment and weather conditions. While the same species of tree will always exhibit similar basic features (such as leaf shape and bark texture), it will develop very differently depending on whether it grows by itself or in a group, is sheltered or exposed to strong winds, is surrounded by plentiful soil and moisture, or has to extend its roots to seek nutrients.
Bonsai can reflect the entire range of ways trees grow in nature, from a striking single specimen or a dense forest of trees, to a wooded landscape on grassland or a craggy mountainside. The basic principles of styling and planting, explained in other posts, help to create a sense of perspective, and an impression of scale and space.
It is essential to study trees in nature when "training" yourself as a bonsai grower. It is not a good idea to use even a fine bonsai as a model for your own tree. That design worked well because of the specimen the grower started with, and the way in which it was trained. You will not be able to reproduce all these elements to "copy" a successful bonsai; instead, you should consider the material you have, and use your experience of natural growth patterns and bonsai training to bring out its full potential.