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Soil and Repotting

Text, and photos by Morten Albek, Denmark
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A trowel is used to get the tree free from the pot, and lifting it without breaking too many of the fine roots.

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 therefore the need for transplantation will be more frequent.


Remember to let the tree dry out before it is transplanted. It should not be totally dry, but it is important that the soil is so dry that you are able to remove it without damaging the roots. Wet soil will take the finest hairy roots with it when removed.

Use a chopstick to clean out soil and roots.

Donít leave any old soil that is claylike and dense in structure, because it will prevent water and air to reach the roots, and they will die.

A chopstick used for a gentle pressure, in order to get the new soil well in between the roots.

Leave a little amount of the old soil , 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 Mychorriza fungi is very important to the Pine tree. It is seen as small areas of white hairy lines around the finest roots.

But never leave 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

The soil I use for my shohins are a little bit different, but it also depends on the species.

In general I am always using small lava pieces or Leca pearls, for drainage layer in the bottom of the pot.

For The Smallest Shohins (Mame)

The general soil-mix is made of:

80% sphagnum moss or peat

20% of fine-grained lava stones, or small Leca pearls.

For Pines and Junipers

80% sphagnum moss or peat

10% lava

10% Pine bark

For The Normal Shohins

The general soil-mix is made of:

70% sphagnum moss or peat

30% of fine-grained lava stones, or small Leca pearls.

For Pines and Junipers

60% sphagnum moss or peat

20% lava

20% Pine bark

Particle Size

The particle size for a shohin-bonsai has to be a little bit finer than for bigger bonsai.

Just use common sense to evaluate how fine it needs to be.

Remember, it is of great importance to keep dust like soil away to prevent the soil from being to compact.

A very dense soil will limit the amount of air and eventually kill the roots. Like in the case of old soil that is very compact and sour.

What About Akadama?

I have to mention, that I never use Akadama. I find it is of no benefit for the plants if they are living in an environment, where the humidity of the air is so much lower than it is in Japan.

Akadama is good where the air contains a high level of humidity. Akadama is clay, and in the start it is very loose, and holds water rather shortly. But in exchange it provides the roots with a very high level of air. That is excellent, but only in an area with very high air humidity.

And all of a sudden Akadama seems to break down. Thereby it presses all the air out of the soil. With fatal results, when the leaves of the plants can't take enough water from the dry air found in most of Europe.

In a dry climate, as in most of Europe, and in places like ours there is a need for a more water holding soil, so it doesnít dry out too easily.

You have to do your own experiences, because local water and surroundings make 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 year or every second year,depending on 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.

The roots are pruned lightly in order to develop new fine water consuming roots, and to prevent the mass of roots to be too dense. At the same time old soil is removed and fresh soil added.

Moss is planted in a bonsai. After a few months it will have developed into a natural appearance.

After the tree is planted it is fixed and secured to the pot with wires and watered carefully. No dry spots must retain in the soil, because the roots will be damaged by it.

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