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Chapter 11 When To Repot Your Bonsai
Bonsai cannot be repotted at any time of the year; for the majority of species,
there is a small period of time during the Spring where the roots can be disturbed
and pruned with reduced risk of danger to the tree's health. Though there are tree
species that can be repotted at other times of the year, the purpose of this article
is to describe and highlight the best time for repotting the typical deciduous
bonsai in Spring. It is well known (and is frequently referred to in the Species
Guides at Bonsai4me.com) that bonsai should be repotted 'when the buds start to
extend', but, what exactly does this mean and exactly when does this happen? It
is not possible to specify exact calendar dates for repotting. Different tree
species require repotting at slightly different times and different trees of the
same species can be ready to repot at slightly different times, even those grown
in exactly same climate. Different climates can dramatically effect the exact date
of repotting; repotting time in Florida will take place weeks before repotting in
New York. However, nearly all tree species follow the same series of stages of
bud growth in Spring and these can be used to identify the best time to repot
your bonsai. This process should be well understood if you are planning on
gifting someone these small potted trees.
Why Repot in Spring?
As temperatures slowly rise in early Spring, the roots of a bonsai slowly
become active. The energy resources of the tree that have been stored in the
roots over winter begin to move back up into the tree. As they do, the dormant
buds on the branches (produced in late Summer and Autumn of the previous
year) begin to swell.
This is the signal that the tree is beginning to come out of dormancy. As
ambient temperatures continue to rise through the next weeks, move of the tree's
stored energy moves from the roots, up into the tree in readiness for the
explosion of new growth as the tree comes into leaf. At this point, the roots stop
being an energy store and their primary function is to supply the newly opening
leaves with moisture from the ground. This process can be followed from start to
finish by observing the state of the buds visible on the branches on the bonsai.
This process can be broken down into 4 stages;