Page 115 - Tài liệu cây cảnh Bonsai4me Bonsai Basics

Chapter 15 Maintenance Pruning 1-

Apical Growth

Bonsai are ordinary tree species that require regular pruning to keep their
diminutive shape. Without pruning, branches extend and the tree begins to lose
its shape. Given enough uninterrupted growth, these branches can eventually
thicken out of scale with the trunk and become coarse. Eventually, if left
unpruned for long enough, a bonsai will simply revert to resembling an ordinary
tree or shrub and the process of bonsai will need to be started again.
To combat this reversion and to keep its shape, a bonsai must be pinched
and/or pruned on a regular basis. This is commonly referred to as 'maintenance

pruning'. The period between carrying out maintenance pruning on a bonsai very
much depends on the species used, the time of year and the vigour of an
individual tree. Identifying whether a tree needs to be pruned though is simple,
and will be discussed in the following series of articles.
These articles are written as a guide to the maintenance pruning of 'finished'
or styled trees; there are however, occasions where uninhibited growth is
allowed. This is often required as 'sacrificial growth' to thicken up trunks or
simply in order to form a new branch or branch structure.
Apical growth

One of the key elements to understanding the pruning of bonsai is 'apical
dominance'. Almost all trees and shrubs, and therefore bonsai, are apically
dominant. Essentially, this means that growth is stronger near the top and outer
edges of the tree. Apical dominance is a mechanism that trees have evolved to
encourage extension of height and width, in order that the tree not be shaded out
by neighbouring plants. It also enables a wider distribution of seed in Autumn so
that their seedling offspring are not in direct competition with the parent tree for
light and water.
A result of apical dominance is that foliage nearest the trunk is eventually
shaded out and dies back. This inner growth is lost at the expense of the ever-
extending apical growth. Normally when growing in the wild, a tree will waste
little energy forming new growth on its inner branches; it will concentrate all of
its resources on the tips of the branches in its continual path onwards and
upwards.