How to Grow Bonsai Trees
Seasonal Care of Outdoor Bonsai Trees
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indoor bonsai care
outdoor bonsai care
navigation to description of roots pruning
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Like other creatures, life activities of plants vary depending on temperature,
humidity, and sunshine. When making a bonsai, you must nurture and
manage the plant as its growth requires. For example, for plants growing in
areas with four distinct seasons, their yearly growths can be divided into the
following several stages.
Winter is when plants lay dormant. Plants store the nutrition produced in the
previous summer in their bodies and enter dormancy in this state. Generally
speaking, nothing but watering is necessary during this period. If your bonsai
tree is deciduous, you can simply keep it indoors or under the eaves. As you
can view the tree's graceful shape during this period, this is the perfect time
for bonsai exhibition.
When winter is about to end and spring returns, plants come to life again.
During this period, you can prune the tree's thick branches, fix the branches
with wires, or repot the plant. These works typically will damage the tree, but
at this stage there is still enough nutrition left in the tree, so the damage can
be kept at minimum. Moreover, when the plant becomes active again in
spring, the damages will be easily repaired. Repotting during this period can
make space for the roots' growth in spring. If your tree is deciduous and has
been kept indoors during winter, you should take it outside the house.
As the weather gets warmer in spring, the plant's growth becomes
increasingly active. Under the influence of the nutrition stored in the body,
new buds and roots grow simultaneously. The soil in the pot also dries up
easily now, so you need to frequently water the plant. After the new buds
appear and new leaves grow out, you can then prune them. For some species
of trees, you need to prune the new buds before the leaves grow out. Since
the tree grows rapidly during this period, you should closely monitor its
growth condition and prune any protruding or unwanted new buds.
Trees grow to the full in summer, and by this time they have depleted the
nutrition stored during the previous year. Meanwhile, leaves growing from the
stem produce nutrition via photosynthesis and the new nutrition is stored in
the plant's body. During this period the tree uses up all the energy in its
growth, and its vitality is low. So you should only water the plant and avoid
other kinds of work. As the soil in the pot dries up quickly, watering is the
main task during this period. When the temperature rises, trees will also
enter a period of dormancy in order to protect themselves. In addition, high
temperature and high humidity can induce diseases and insect pests. Since it
is difficult to cure trees plagued by pests, everyday prevention is crucial.
In autumn, the growth of branches and leaves slows. As the plant needs
less nutrition for its growth, the rate of storage of nutrition produced in the
leaves accelerates in the body. This is the best time for the tree to replenish
its vitality. If you have a pine tree, it is also the time to create its shape by
wiring. As the temperature in the soil is higher than that on the surface of
the soil, the roots are still growing. So this period is also suitable for
repotting. After repotting, the roots will keep growing in the soil and firmly
take root there. To maintain sufficient vitality of the tree, you may consider
fertilizing it. After the red leaves of a deciduous tree fall, you can have a clear
view of the tree's shape. So this is the perfect time to prune the small
branches. You should prune the protruding branches that disrupt the tree's
shape and any other unneeded branches. Finally, the tree enters dormancy in
Plants that grow in bonsai pots must be repotted from time to time. The
growing roots of a plant will occupy the limited space in a pot and thereby
reduce the free space for the plant to develop. In addition, as time goes by,
the soil in the pot will become hard and less permeable for air or water.
These conditions will lead to poor health of the plant and the plant may
even wither and die. So, it is necessary to repot a bonsai plant. Moreover,
repotting provides a good opportunity to
prune the roots and shape the
Repotting consists of three parts. The first is to remove the necessary
amount of old soil and replace with new soil. The second is to prune the
plant's roots. The third is to determine the planting angle and repot the plant
into an appropriate new pot that best presents the tree's beauty.
When the roots in the pot have no place to grow, or the soil becomes hard,
therefore water cannot permeate the soil during watering and remains on the
surface of the soil, you need to repot the plant. In general, you need to repot
young evergreen conifers such as pine trees once every two to three years,
and once every five years for adult trees. You need to repot young deciduous
trees once every year, and once every two to three years for adult trees. Of
course, the frequency of repotting depends on the tree's living environment
and the climate conditions. For example, in harsh climate the tree's growth is
slow, so you should reduce the repotting frequency.  
You should conduct repotting when it brings the minimal damage to the
plant. Typically this is before the buds emerge in early spring or after the
buds mature in early autumn. The best time is early spring. If you repot the
plant during this period, not only will it bring the minimal damge to the tree,
but also the tree's roots that are pruned during repotting will grow rapidly
afterwards. In this way there is minimal obstruction to the tree's growth.
Should you choose to repot at other times, you should avoid pruning the
roots as much as possible.
You need to gently knead out the roots and clean up the old soil on them.
When doing so you must be sure not to damage the fine roots. You may find
root rake or a bamboo chopstick to be very handy. If the soil surrounding
the roots lumps together, you can use awl, bodkin, ice pick, and tweezers to
remove it easily. You should start this process from the bottom of the roots,
then work on the vertical cross sections, and in the end clean the top part. In
this way you achieve a thorough cleaning.
For young evergreen conifers such as pine trees, you typically need to
remove about half of the old soil. You remove about one third for adult trees.
For deciduous trees you can remove more old soil. It is typically two thirds
for young trees and about a half for adult trees. The picture here shows a
young deciduous tree with two thirds of the old soil has been removed. The
exact amount of soil can be removed before the roots wither depends on the
tree species. Take for example the deciduous Acer (Maple), some trees may
not wither even after you remove all the soil.
After you clean up the soil, you will have a clear view of the roots. Now you
prune the roots for pruning old roots can promote the growth of new
roots. Root pruning is done in the same way as branch pruning. You should
spread out the slender roots. Therefore, you should prune the long and thick
roots, the entwined roots, and the upward-growing roots. Since water is
absorbed from the root tips, in the limited space of the pot, plenty slender
roots are better at absorbing water than few long and thick roots. Therefore,
you should prune all thick roots such as the tap roots that grow vertically
When you prune the upper half of the roots, you should decide which part to
be exposed from the soil. In other words, you should decide the height of the
exposed surface roots (“
nebari”). You need to prune the roots that are
higher than this level, and for “
happo-bari”, spread the roots evenly in
various directions starting from where they touch the surface soil. You also
need to prune any unnecessary roots and “
imi-ne” (dreadful roots).
Repotting is done in the following order. You first
put a
screen on the drainage hole in the bottom of
the bonsai pot and lay down the
wires that will be
used to fix the tree. The screen keeps out the
insects. You then lay course
soil (“goro tsuchi”)
whose grain size is about 1/4"(6 mm) or more in
diameter. On that you lay planting
soil (“ue
”) whose grain size is about 1/32"~1/4"(1~6
mm) in diameter. - Grain size in
Shohin bonsai
(shorter than 10") is a little bit smaller overall.  
Now you place the tree on the planting soil firmly.
Before fixing the tree with the wires next you
should make sure there is no gap between the
bottom of the tree and the soil. You then add
more planting soil evenly, insert a bamboo
chopstick, level the soil and fill all the gaps. When
adding the soil it helps to gently knock the side of
the bonsai pot. Since water and air cannot
permeate the soil whose grain size is smaller than
1/32"(1 mm) in diameter, you must sift away these
tiny soil grains. Even the best soil dries up every
To prevent the soil from turning over due to
watering, you can lay some
mosses or gravel on
the surface soil in the pot after you have finished
the above work. In the end, you need to water the
plant in the bonsai pot until clear water flows out
of the drainage hole.
During the two to three weeks after repotting, you
should leave the plant in shaded bright area and
let it avoid sunshine or wind. You should make
sure the plant is not too dry, but you should not
fertilize it before the roots grows.
In general, for repotting you should
choose a new bonsai pot that is slightly
wider than the tree. In this way the tree
and the
pot are proportional in size. It is
also believed that this creates wider view
of what is behind the tree. If you want to
use a larger bonsai pot for repotting, the
pot should be one size larger than the
former one. Oversized bonsai pot will
reduce the beauty of “
ne-bari” (the
adhesion of the roots) and make the soil
less likely to dry, which can cause the
roots to rot. On the other hand, if you
want to use a smaller bonsai pot for
repotting, you need to repeatedly repot
the plant and prune its roots. This
increases the amount of slender roots of
the plant and improves the water
absorption rate in the pot.
When planting the tree, you should place it in the bonsai pot so as to view
the tree's best shape from the front. Therefore, you must decide which part
of the tree will be its front and at which vertical angle the tree is to be
appreciated. Different viewing directions and different planting angles creat
bonsais of distinct shapes. Therefore, you must imagine the shapes of the
tree's trunk and branches after they grow more and think of which planting
will best display the tree's beauty. To achieve this, you will need to develop
rich imagination, appreciate more excellent bonsai, and cultivate your
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