Page 89 - Tài liệu cây cảnh Bonsai4me Bonsai Basics

Chapter 13 Bare-rooting A Bonsai

After a number of years in a pot, all soils begin to break down and congeal.
Soils that have broken down become dense and airless. The majority of the old
soil is removed during the normal course of repotting, however the inner core of

old soil around the base of the tree and in the centre still remains and it is
important that this is removed and fresh soil introduced on a regular basis. If
poor-quality or old soil is left around the centre of the rootball, it will eventually
cause root rot as well as reducing the amount of healthy soil for the bonsai to
root into and therefore the uptake of moisture and nutrients by the rootsystem. It
would not be unusual for root rot to occur at the very centre of the rootball
attacking the nebari/trunkbase whilst the exterior roots remain healthy.
If you suspect that a tree has a weak rootsystem but can see no obvious sign
of ill-health around the periphery of the rootsystem; bare-root the tree and check
the condition of the inside of the rootball. It is important that bonsai are
completely bare-rooted to remove all old and tired soils at least every 5 years.
Unless you are very certain of the soil used throughout the pot, any newly
purchased trees should be bare-rooted at their first repotting. Field-grown and

most collected trees/yamadori should also be bare-rooted before potting up. All
mallsai are normally grown in very poor soils (particularly those bought in the
UK) and should be bare-rooted during their first repotting.
One major advantage of bare-rooting a bonsai is that it is easier to study the
rootball and remove unsuitably placed roots around the nebari and inspect for
any damaged roots. Deciduous and broadleaf trees can be bare-rooted without
any detriment to their health; more care must be taken with coniferous species
such as Junipers and Pines. I would recommend removing old soil in stages,
approximately a third every year,. Remove the soil by hand and never rinse the
roots with water.
After bare-rooting, extra care must be taken that soil is introduced all the
way around the bare rootball. Use a soil that is dry as it is easier to introduce and
gently work it in and around the rootball with your fingers and a chopstick. After
repotting, water the soil very thoroughly so that no air pockets remain.
Bare-rooting an Elm bonsai