Planting mediums

Dick · Posted: Fri Nov 25, 2005 1:38 pm Post subject: Planting mediums

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Planting mediums
One question that always seems to recur among bonsai hobbyists is, "What is the best bonsai soil to use?"

First of all, to answer that question, there is no one soil that is preferred among growers or hobbyists. Commercial bonsai soils are available from landscaping nurseries and garden centers and each commercial product has its own blend of soil components that are used. Second, for some trees, there are some soil components which will be more suitable for particular trees. Third, many bonsai hobbyists and growers will tend to mix their own bonsai soils rather than look for commercial mixes. Two products commercially available as "bonsai soil" are sold under the names akadama and kanuma, which are inert, having no feed value. These are useful for some bonsai applications, but usually they may be incorporated into a general mix to add to the porosity and/or water retention properties of the soil. This post addresses a general bonsai soil mix that anyone can create for their own use. It also addresses some unique soil needs that can be added to the general mix for some particular bonsai trees.

The first assumption with any bonsai soil is that it should be rather porous so that water will freely drain through it and out of the drainage holes. When watered, the porous soil will assist in drawing air into it rapidly as the water drains through the pot. This is beneficial for the health of the roots of the bonsai tree. Fine particulate matter is not generally part of most bonsai soils mixes since it inhibits the free flow of water through the soil mix. Therefore, if one were to mix their own bonsai soil, they should expect to screen the individual components in order to remove the fine particulate matter. The soil's appearance will be fairly coarse looking.

For a good general soil mix, there are three soil components, each in a 1:1:1 ratio. After these three have been screened, the size of the particles of soil should be roughly 1/8 to 1/4 inch (3 - 5 mm) in diameter.

The first component is sand. This can be obtained from building and construction suppliers or even dug from creek beds or lake front natural beaches. Seaside beach sand has salt in it and is not good for bonsai trees unless it is thoroughly washed to become salt free. The sand should appear sharp in texture once screened. The second component is a calcined clay. There are many commecial clay products available which can be obtained from garden centers that go under various brand names. Here in the United States, Turface and haydite are two of these products. Some people have even resorted to fire clay cat litter in a kiln for bonsai soil mix purposes. The third component is an organic material which the tree will need for some of its nutrients. However, this organic material does not provide all of the nutrients for the tree and so supplemental fertilizing is needed. The organic materials that are often used are regular compost, though not the variety that is sold for gardens due to its fine texture, coarse peat or chopped sphagnum moss, chopped tree bark, etc. Once each of the components are measured exactly in the 1:1:1 ratio by capacity, they should be thoroughly mixed to equally distribute the three components throughout the soil. This forms the composition of a general soil mix that can be used for many bonsai trees just as it is.

jimothy · Posted: Mon Jan 23, 2006 2:43 pm Post subject: Re: Planting mediums

A couple of notes about ingredients for UK residents:

1 - for "sand" in the above article read "grit" - this is best found at garden centres, where it should be washed and graded to 3-5mm or there abouts. Alternatively buy "Sharp sand" which is a mix of small grit and finer sands, but this MUST be thoroughly sifted to remove any particles smaller than 2mm (which will account for approximately half the volume. DO NOT use "builder's sand" in the UK - it contains a lot of lime (calcium carbonate) which makes the mix very alkanine - not good.

my prefered grit is Westland horitcultural grit which is washed and graded to exactly the right size for bonsai use. Find your nearest stockist here: http://www.gardenhealth.com/where_to_buy/index.php

2- Haydite and turface are not available in the UK - use pumice, akadama (available from bonsai-specific stores) or Tesco's "premium lightwieght" cat litter (which is already baked hard so needs no further firing)

3 - one of the best sources of composted chipped bark is B+Q's own brand "Soil Improver" made of composted chipped bark. It needs sifting to remove fine particles, but the majority of what's in the bag is the right size for bonsai use, alternatively buy some peat-free compost, which is mainly made of small particles of composted bark.