Interesting Articles

                           LET”S DO BONSAI!

A normal human being, with a horticultural bent,

When put into a garden, will be quite content

To cultivate some shrubs or even mighty trees

And let the branches reach the sky and catch the evening breeze.

But if the tree should get too big, and have to be confined

They go down to the garden shed to see if they can find

An axe sharp enough to lop a limb or three

Then they set to work and hack the guts out of the tree.

It is all very macho, to see the wood chips fly

And the task is deemed successful if the damn tree doesn’t die!

But there is another breed who are somewhat obsessed

In keeping every plant they own in micro and compressed.

They grow things in tiny pots that stand in tidy rows

Then cart them around the neighbourhood and enter them in shows.

They spend hours with their plants, training every twig

To bend this way or that, and not to get too big.

They tie them up, wire and every leaf is trained

To follow in a pattern with an Oriental name.

You won’t find the tools they use in some old dusty shed

Like a surgeons’ instruments, they’re kept sterilized instead.

The Bonsai grower uses words like “shari” or a “jin”

And no-one knows just what they mean, and so you cannot win

If, as an innocent like me, you strive to start debate

On the pro’s and con’s for growing oak trees on a plate.

But as a hobby it seems harmless, so as a group they’re free

To while away the hours with their teeney, weeney trees.

By Jay Kayess (aka Joyce K Skinner)




 Firstly, I must caution that there are as many different bonsai soil mixes in the world as there are muffin recipes and many of them work well. If your bonsai are growing fast, are strong and healthy and pest free, then don’t change your mix. But, if you are one of the many people I have spoken to recently who has lost one or more of your bonsai from root rot, or you can no longer source the components of the mix you used to use, then you need to consider the points below.


These are Support, Nutrition and Protection.  The soil stops trees from falling over, it stores nutrients, air and moisture and releases them to the plant as required and it acts as a blanket to protect roots from sun, wind and predators.


A pot is a very small area and the roots cannot travel to seek water, air and food like they can in the open ground. They are trapped in the pot and rely totally on their ‘Carer’ for food, water and healthy soil. If very fine soil is used it will compact over time and hinder drainage and suffocate the roots. When a tree is planted in the open ground its roots will travel to find the nutrients and soil it requires for good health. Some of the Australian natives send roots out for kilometers.


This Varies between water loving plants and plants that prefer a drier soil, but water loving plants and deciduous trees can tolerate a finer soil mix than plants like pines and junipers. Some growers sieve their mixes and others do not, but we should all sieve our soil. Sadly, not enough attention is given to soil. People buy the cheapest and nastiest potting mixes, thinking they are saving money instead of thinking about what the bonsai is worth and giving it the best they can afford.

 A large number of Bonsai Masters around the world consistently tell us to sieve our soil and discard the particles that drop through a 1mm sieve. I recently tested three well known Commercial Bonsai mixes and found that up to 55% of the mix fell through the 1mm sieve. So if you use one of these mixes you should be throwing half of it away.  However most people use it straight from the bag and so risk losing trees from root rot. Even if the trees do not succumb to rot the very fine soil will slow down the growth of the tree. One of the mixes I tested had smooth round pebbles instead of sharp porous ones. Particle sizes in a good mix vary from 1mm to 6mm.

 It is important when mixing soil to avoid or delay compaction and create good drainage. The lack of one or both will see roots suffocate or drown, either way they will probably die. An OPEN MIX contains more large particles and drains freely and quickly. Trees grow faster in an open mix so it is recommended for trees in training.  A CLOSED MIX has a small particle size and drains slowly. Trees grow slowly in this mix so it is better for old trees in refinement (provided it still drains well) and the ‘Carer’ understands the watering issues.  (Note that a lot of this information came from Japan where their old trees are hundreds of years.) 

Comments like “I have a really good mix, it holds water for so long I only have to water once a week” will usually see tree fatalities within a couple of years as the roots drown. The faster the excess water drains away the healthier the bonsai will be. As the water drains down through the pot it pulls air in after it enabling the roots to drink and breathe. Soil that stays wet for several days stops the roots from breathing and downs them.


The major thing that confused me when I first started bonsai was the terminology “sand”. I knew the books didn’t refer to ‘beach sand’ as the salt content would be too high, but I did think that was the particle size we should use. I later found out that by ‘sand’ the Japanese mean small river and mountain stones of about 2 to 6mm!! I would recommend that a grower purchase a set of sieves and experiment until they become familiar with the look of particle sizes. Components such as scoria (crushed lava rock) decomposed granite, diatomite, zeolite, turface, perlite and river sand all meet the trees’ needs, providing the particle size is between 2 and 6mm. I have had success using 40% Diatomite (like turface) 20% zeolite, 20% chopped sphagnum moss and 20% premium potting mix. I had previously used Scoria instead of Diatomite but it became hard to source so I have changed, but now the provider of Diatomite has closed down also so I will change back to Scoria!

 Boon Manakitivipart, an International Demonstrator,  says not to use premium potting mixes as the bark has not always composted properly and becomes acidic as it compacts. Also pine bark compacts too fast, causing need for repotting sooner. Boon does not use sphagnum moss in his mix but suggests using a fine layer chopped and spread over the surface after repotting to hold the moisture in and protect from the sun. When we were in Melbourne at the AABC convention in May I met Boon who was the International Demonstrator and discussed soil mixes with him. I then emailed him and he has guided me with the components for my mix. He also said that we could grow healthy bonsai by using either scoria or Turface on its own!!

 I have bought 2-5mm scoria, 2-5mm Turface MVP and 4-6mm Zeolite. I am now using equal parts of these products for my mix plus a little horticultural charcoal. Combined with the nutrients in the mix and the fertilizer I will add, I believe I should have healthy fast growing bonsai. I believe this open mix actually saves water as it runs through so fast that it doesn’t take as long to saturate everything in the pot. It still holds enough moisture to keep it damp all day and as I said earlier, healthy soil drains fast . The beauty of using a mix like this is that while it may be expensive to start with, it can be recycled so eventually becomes very economical to use. It is quite light so assists with the overall weight of the tree in the pot. It is not my intention to convince bonsai lovers to use the same mix as I am using, instead I hope I have caused people to think hard about the health of their bonsai and the soil mixes they use and to search out more information on soils.


Care must be taken when going from a mix with a lot of compost and fine particles to one that is all stone and pumice. All the old soil must be removed from the roots and this isn’t a problem with most deciduous trees as they can be bare rooted and washed, but care must be taken with pines and junipers which cannot be bare rooted and washed as it would remove the micorrhiza which is necessary for healthy roots. Boon told us that when introducing a pine or juniper into a mix like this he removed all the soil from one half of the bonsai and left the other side, then repotted it and the following year he bare rooted the other side. He did not wash the roots!

REMEMBER the old saying, “If it ain’t broke, don’t fix it.!

 So don’t change your mix if your trees are healthy.  My only reason for changing my mix was because the product I was using was no longer available!!