An Introduction to Bonsai Soils

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Bonsai Soil Mixes In The UK Available From The

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Bonsai Soil Mixes In The UK Available From The

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Sifting out ‘Fines’

Large amounts of dust that remain in the soil mixture can clog the open structure of the soil and disrupts the drainage of excess water. For a good soil structure that drains well, where necessary, soils are sifted to remove dust and very small particles.

Switching From Organic To Inorganic Soils

Almost all deciduous varieties will tolerate the transition from organic to inorganic soils immediately; coniferous species, in particular Pines and Junipers, require the retention of some of their old soil which will contain the mycorrhizae fungi necessary for their survival.

The Best Soil Mix for Bonsai

There is no single soil mix that is best for cultivating bonsai; variables such as local climate and rainfall, personal watering regimes and individual tree species all contribute to variations in enthusiasts’ soil mixes.

My personal favourite soil mixes at the time of writing (November 2021) are from Ibuki in Poland and are a mixture of akadama and volcanic inorganics such as pumice and lava rock. The pumice and lava provide excellent structure ensuring aeration and drainage while the softer akadama particles are excellent for the fine roots within the rootball to root into. Chopped bark can be added to 'fill out' the soil for better water retention in deciduous trees and additional lava rock can be added for a drier mix suitable for coniferous species.
I use medium-sized particles 4-5mm in size for most trees, with a soil surface of smaller (2-3mm) more water retentive particles. For coniferous species such as pines I will add larger 6-7mm particles for more drainage.

Ultimately, experience of using different soil types and ingredients will shape your own particular preferences. It is recommended that, in the first instance you find out the soil-mix that local enthusiasts are using and take it from there.
I would however always recommend that an inorganic soil be used to improve the health and ease of cultivation of your bonsai.

‘Bonsai Soils’ bought from Nurseries and Garden Centres

Though it saddens me to say this, the vast majority of products packaged and sold as ‘bonsai soils’ at plant nurseries, garden centres and even some bonsai nurseries are next to useless for bonsai. Often these are simply peat/ compost based soils mixed with some sand or grit and (as described previously) have a soil structure that is too water retentive, airless and generally bad for the health of your bonsai.

There are of course knowledgeable outlets selling good quality soil products. However, just because you bought some ready-mixed bonsai soil from a nursery does not necessarily make it suitable for the health of your bonsai. Similarly, if you have bought a bonsai from anywhere other than a well-respected specialist bonsai nursery that will care about the quality of the trees it is selling, do not assume that the tree is planted in a good soil.

Feeding Trees Growing In Inorganic Soils

If there is one thing that seems to worry enthusiasts about switching to an inorganic soil is the lack of ‘proper’ organic and a ‘lack of nutrients’. Firstly, I and many (most) experienced enthusiasts have switched to largely inorganic soils (such as lava, pumice, Akadama etc) and have been using these products for many years. The reason for switching to inorganics is purely for the increased health, vigour and strength that it provides a bonsai (or any plant for that matter). Be confident that switching to inorganic soils is widely considered ‘best practice’.
Bonsai grown in an inorganic soil do not need any special fertilising regime or special ingredients to keep them healthy. There are of course some differences between compost-based organic mixes and inorganic mixes. Inorganic soils contain little or no nutrients, however, compost/ peat based organic soils just as equally only provide very limited nutrients to a bonsai and these are quickly depleted within a bonsai pot.
Organics are able to retain more nutrients better than inorganic’s, after feeding, but this is not necessarily a good thing. Trees growing in inorganic soil need more fertiliser than those growing in an organic soil. Many enthusiasts see this as being advantageous though as it allows the enthusiast to feed their bonsai heavily to encourage better growth, health and faster development. That an organic bonsai soil can hold nutrients for a little longer than an inorganic bonsai soil is hardly advantageous, as bonsai growing in organic soils still need to be fed regularly!

Related Article: Soil Mixes for Weak and Newly Collected Trees and Yamadori Aftercare

Bonsai Soil Mixes In The UK Available From The

bonsai4me shop
Bonsai Soil Mixes In The UK Available From The