Soil and transplanting

There are some quite different demands to the choice of soil for Shohin- and Mame-bonsai, compared to bigger trees in bigger pots. All together it can be summed up in two main differences:

1) Shohin-bonsai are living in a very limited amount of soil, and space, and are therefore drying out quicker than bigger bonsai.

2) The soil is filled up with roots from the plants faster than big bonsai, and the therefore the need for transplantation will be more frequent.

Roots pruned.
Roots pruned.

Use a chopstick to clean out soil and roots. Don’t let any old earth be that is clay-like and dense in structure, because it will prevent water and air to reach the roots, and they will die.

Let a fair amount of the old soil stay, when the tree is transplanted. Especially when transplanting Pines, it is of importance to let some old soil be around the roots. Because the white Mykhorriza fungi is very important to the Pine tree. It is seen as small areas of white hairy lines in the soil between roots. But never let clay like soil, or very compact soil, stay in the pot. It is essential for a bonsai to be able to let the roots breath so to speak. Air is a very important factor of the environment in the pot, in order to keep the roots healthy.

Remember that also the new soil used at the transplanting, has to be very dry. The soil I use for my Shohin is a little bit different, but it also depends on the specie. In general I am always using small lava pieces or Leca pearls, for drainage layer in the bottom of the pot. (Leca are a hard burned pill of clay, which are totally steady in structure, and retains a high volume of oxygen. Lava grid in smaller pieces can be used instead of Leca).

The particle size for a Shohin-bonsai has to be a finer than for large sized bonsai. Just use common sense to evaluate how fine it needs to be.

Here is a basic guideline of my soil mixes, but you have to adapt this to your own experience and growing conditions.

Basic soil components that may be adjusted individually for each tree.

 

Large bonsai – deciduous soil

50% Akadama or equal

25% Pumice or equal

25% Organic or lava

 

Shohin bonsai – deciduous soil

30% Small sized Akadama or equal

35% Pumice or equal

35% Organic or lava

 

Shohin Conifers

30% Akadama (small size)

25% Pumice or equal

25% Lava rock or equal

20% Organic

 

Bonsai – large – conifer soil

20% Akadama (small size)

35% Pumice or equal

25% Lava rock or equal

20% Organic

 

Remember it is of great importance to keep dust like soil away from Akadama (often present with Akdama of a poor quality), to prevent the soil from being to compact. A very dense soil will limit the amount of oxygen, and eventually kill the roots when waterlogged. Like in the case of old soil that is very compact broken down.

You have to do your own experiences, because local water and surroundings makes differences that can be quite extensive. This is just a guideline. Because of the limited room a Shohin-bonsai lives in, it is necessary to repot every one or second year. Depending of how fast the tree grows, and the size of the pot.

It is necessary to repot more often than in the case of bigger bonsai, in order to keep a constant developing of new fine water consuming roots.

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