Page 39 - Tài liệu cây cảnh Bonsai4me Bonsai Basics

to their habitat and the quantity of water that is available to them. If there is not

enough water available to the root system, the roots will spread out into the soil
until enough moisture can be reliably acquired. Thus plants growing in relatively
dry areas will have far-reaching root systems that will continue to spread out
until a reliable source of moisture can be found.
On the other hand, trees growing in damp conditions where moisture is
permanently available in the upper levels of the soil, will tend to have shallow
root systems as they have easy access to moisture.
In the confines of a pot, a bonsai loses this ability to self-regulate its
exposure to moisture. It is unable to govern how much or how little water it
accesses. The compost in a bonsai pot is also far less stable than soil in the
ground, the possibility for it to dry out is greatly increased and it is greatly
affected by the outside influences such as the weather and the surrounding
ambient temperature.
Correctly watering your bonsai is a skill itself and is not as straightforward
as one might expect when first starting out. It is often said in Japan that it takes 3
years to learn to water correctly. It can sometimes take three years of tree losses

before a bonsai enthusiast realises that it is his/her watering regime that might be
the cause!
The Effects of Under-and Overwatering
Plants rely on a continual flow of water to stay alive and to grow. Water is
absorbed from the compost into the roots by a process known as osmosis, the
water is then pulled up the body of the plant and is released into the atmosphere
through the foliage. This process allows the plant to distribute vital nutrients
throughout its structure. However, without a source of moisture at its roots, this

flow of water is interrupted and the plant structure quickly collapses and dries
out. Leaves and branch tips are the first areas to be affected, followed by
branches. Finally the trunk and roots themselves collapse and dry-out by which
time it is unlikely that the tree will survive without damage. Application of water
at this point is often too late; moisture can actually be absorbed out of the roots
back into the wet compost in a process known as reverse osmosis.
As previously mentioned, the effects of overwatering a far more subtle and
can take a relatively long period of time to detect. Overwatering creates an
environment for the root system that is permanently wet. Roots need oxygen to
'breathe' and the presence of too much water reduces the ability of the compost
to absorb air. This in turn causes the fine root hairs to suffocate and die. The
immediate effect to the tree is a loss of vigour as parts of its root system are
unable to grow and/or dieback.