Cat Litter as Bonsai Soil (Diatomaceous Earth or 'Diatomite')

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Bonsai Soil Mixes In The UK Available From The

bonsai4me shop
Bonsai Soil Mixes In The UK Available From The

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For many years I used Tescos' 'Low Dust Lightweight Catlitter' as a very useful way of improving the soil I was using for my bonsai. I still have a good number of trees that have cat litter at the core of the rootball and I see no reason to try to remove it; it does what it was supposed to do which is keep the soil well-drained and aerated.

But back in 2000-2001 when I was first told about using this high-fired clay for my bonsai, thimngs were very different. We had two major problems with bonsai soil in the UK, and without doubt across the world given the huge response to this page when I first published it.
Firstly at the time, people were still using peat and grit, John Innes, sand, all the types of soil that ordinary gardeners would use for their potted plants. These mixes were utterly dreadful for bonsai (and I see some people still using things like this, even now, 20 years later!). Using a high-fired clay such as catlitter, importantly, with the addition of chopped bark for the roots to grow into, was a huge advancement. We suddenly had a substrate that encouraged strong rooting, good drainage and most importantly, dissuaded rotten roots.
Secondly, the only alternative at the time was akadama. An expensive soil that was difficult to obtain unless you happened to live near a bonsai nursery. (Bear in mind, 2000 was also the early days of the internet and it wasn't totally straightforward to order anything online). The trouble with akadama was also that if used on its own, without additional components such as pumice or lava to provide structure, it would just breakdown and solidify, leaving a badly-drained and airless soil.

So in those days, this particular brand of catlitter really was a godsend, particularly as I started collecting large numbers of trees that required large amounts of bonsai soil. It really wasn't any wonder that the use of catlitter exploded in bonsai!

But times change and we've now hit 2021.

There are now much better soil components available for us to use, and they're easily available to order online. I find that if you can buy in bulk, pumice and lava are very similar in price and the convenience of having it delivered to your door (should you wish) makes them the ideal components to mix your own soils. Akadama is still relatively expensive, but as something to add to pumice or lava, it goes much further than the days when it would be used neat and undiluted. Bark chippings can still be used as an equivalent; vegetative-based particles that do not clog up the substrate as a whole.

The major problem with catlitter:

The grain-size of catlitter became much smaller over the years, sometimes down to as little as 1-2mm, too small to encourage proper drainage. Although if you used bark chippings as recommended, this wasn't the end of the world.

The major problem with diatomite-based catlitter is that, as I discovered, it is derived from fossilised sea creatures that have anti-fungal and insecticidal properties. In these modern times of bonsai cultivation, we are trying to enhance the health of the soil or biodome into which the roots of our trees grow. We are now adding live bacteria, mycelium and fungi to encourage strong and better growth habits in our trees. Diatomite does not aid this, rather it can negatively impact the natural fungal and bacterial health of the soil structure.

If you are still using catlitter, I would encourage you to now look at switching to a pumice-based soil, or at very least, add pumice to the mix alongside the chopped bark. Your trees will love you for it.

If you would like to know more, please visit this newly updated article on Bonsai4me: An Introduction to Bonsai Soils

If you are wondering about my personal soil mixes for 2021-2022, here they are:

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.

Bonsai Soil Mixes In The UK Available From The

bonsai4me shop
Bonsai Soil Mixes In The UK Available From The