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

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Areas outside the UK

To find suitable alternative brands outside the UK, you must be prepared to try a number of products until you find the correct material. This can be difficult, as very few makers of cat litter will display the ingredients on the outside of the packaging!
Avoid all products containing paper, wood chippings or Fullers Earth as these will swell when wet. Also avoid the cheapest clay products as these are more likely to contain unfired clay granules.
Unfired clay granules swell and clump together when wet and crumble when dry. As the granules break down and congeal they will do great damage to the roots of your tree, causing the roots to rot and the tree to die. Watering properly will be virtually impossible. It is of maximum importance that any cat litter clay granules you use keep their structure indefinitely.
To test a new product for its ability to retain its structure, first soak some of it in water for 24/48 hours and check that the granules do not break down. Then try putting the wet granules into the freezer for a few days and see if they retain their structure after thawing out. Reject any products that break apart. To illustrate how strong the 'Low Dust Lightweight' granules I am using are, they are impossible to break between the finger and thumb, even when wet or frozen.
Finally if you have any doubts, use the granules for cuttings and seedlings at first; these will react to anything 'bad' in the soil quickly and their loss can be taken much more easily than if you lose a bonsai.

Perfumed Cat Litter

Many Cat Litters are perfumed; the perfumes themselves should create no problems as they are quickly dissipated after contact with water. If in any doubt, watering the mixture a week before use will release most, if not all of any residual perfumes.
Some products can also contain baking soda, this is used by the manufacturers to neutralize odours. Baking Soda is far more 'stable' in the soil, that is, it will remain in the soil for longer than any perfume will. However, all of the research I have been able to obtain indicates that baking soda has actually been long used as a fungicide against mildew in roses and other members of the rosaceae family (Hawthorns, Crab Apples etc).
According to Cornell University research, the only plant damage associated with baking soda/Sodium Bicarbonate in tests, resulted from some foliage burn when the leaves were sprayed with a highly concentrated dose of Baking Soda.
The Cornell testing also established that Sodium Bicarbonate does not increase the levels of Sodium in plant tissues, soil or run off water.
Sodium Bicarbonate is an alkaline substance but in cat litter it appears to be in too small a quantity to effect the pH of the soil. My understanding is also that though Sodium Bicarbonate will neutralise acids it will not increase alkalinity.
However, I do have to recommend that if using any brand of catlitter for the first time, check the pH of the soil. In the case of Tescos 'Premium Lightweight' cat litter, all tests I have made have shown a neutral pH of 7.

Feeding Trees Growing In Catlitter (and all other 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 catlitter, baked clay, akadama, turface etc etc) entirely and have been using these products for many years. The reason for switching to inorganic's 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's need (but can also take without any danger of root burn) 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!

With my inorganic soil mix, I am able to feed heavily and use (as do many) a slow release fertiliser and a fortnightly full strength balanced plant fertiliser simultaneously throughout the growing season.

Finding Other Sources

Since writing this article a number of years ago, I have received several e-mails from bonsai enthusiasts outside the UK trying to find a suitable cat-litter/fired clay product to use as bonsai soil.

Fortunately I have received some very useful information from bonsai enthusiast Tim Riley who has done some research into 'Tescos Low Dust Lightweight' and has discovered other possible sources for those outside of the UK.

My thanks go to Tim for making this information available.

Tescos Low Dust Lightweight cat litter is a 'Moler Clay' and originates from Denmark, exported by a Scandinavian company - Damolin. Moler Clay is a type of Diatomaceous Earth or 'Diatomite'. "Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. It is used as a filtration aid, as a mild abrasive, as a mechanical insecticide, as an absorbent for liquids, as cat litter, as an activator in blood clotting studies, and as a component of dynamite. As it is also heat-resistant, it can be used as a thermal insulator."
"Freshwater diatomite (Diatomaceous Earth) can be used as a growing medium in hydroponics gardens.
It is also used as a growing medium in potted plants, particularly as bonsai soil. Bonsai enthusiasts use it as a soil additive or pot a bonsai tree in 100% Diatomaceous earth. Like perlite, vermiculite, and expanded clay, it retains water and nutrients while draining fast, allowing high oxygen circulation within the growing medium."
"Its absorbent qualities make it useful for spill clean-up and the U.S. Center for Disease Control recommends it to clean up toxic liquid spills.”“More recently, it has been employed as a primary ingredient in a type of cat litter. The type of silica used in cat litter comes from freshwater sources and does not pose a significant health risk to pets or humans." (Source: http://en.wikipedia.org/wiki/Diatomaceous_earth)

So essentially, if you are unable to obtain 'Tescos Low Dust Lightweight' cat-litter (moler-clay/ Diatomaceous Earth/diatomite) what other product names is it sold as? In the UK there is a product called Sophisticat Pink cat litter that is sold at 'Petsmart' and 'Pets at Home' and it is exactly the same clay granules as those sold as 'Tescos Low Dust Lightweight'. (Interestingly, there are a few references online to experienced UK bonsai enthusiasts that have been using Sophisticat Pink cat litter to good effect for many years).

Don Smith aka 'Stymie' from the South Yorkshire Bonsai Society has e-mailed to let me know he has been using cat litter to good effect for 4 years now and has found that Sophisticat Pink which has varied size grains (unlike the standard round pellet of Tescos Low Dust Lightweight), the majority of which are larger than those now found in Tescos product.

Sophisticat Pink is imported into the UK by a company called Steetleys who are bagging it up under a number of different product names. It is very possible that there are other UK chain stores other than Tescos that are selling the same product as Sophisticat Pink and Tescos Low Dust Lightweight under different 'own brand' packaging.
So Steetleys are importing from a Scandinavian company Damolin and bagging it up under different names. On the Damolin site it appears that French & German subsidiaries distribute Damolin cat litter for the rest of Europe.A Google search for Diatomaceous Earth and/or diatomite (as it is also known) throws up many different sources throughout the world. I would recommend searching online for Diatomaceous Earth and/or diatomite products in your country. These will be sold as cat litters, oil-absorbents, soil conditioners or as hydroponics products.

You may be very surprised to find that a cheap, easily sourced and high quality bonsai soil can be bought in your local pet shop or supermarket!Please ensure that you check the suitability of any products that you obtain using the method described elsewhere in this article and try growing some seedlings or young plants to test your new 'soil' before using it for a prized tree! If you discover that the product is suitable as a bonsai soil; please tell me so I can list it within this article for the benefit of other enthusiasts!

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