Can I use cat litter in potting mix? Has anyone tried it?

Question

I've read in some bonsai forums that it's possible to use cat litter in alternative to the traditional bonsai soil, which is really expensive.

I want to try it in the potting mix I'm making for my interior plants. Does it really work? Has anyone tried this?

I was thinking maybe something in the following ratio:

Cat litter              50%
Perlite                 30%
Some organic (compost)  20%

I'm adding the perlite because cat litter is kind of heavy. Also, I'll be fertilizing it as needed.

The reason I'm willing to try it, it's because I tend to over water my plants, and I'm looking for a soil that will absorb some water, but will drain the excess, which seems to be the case for cat litter, otherwise bonsai growers wouldn't be using.

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I know there are at least two types of cat litter.

There is a "clumping" type, which is made mostly of bentonite, and it clumps in the present of water, which is a great feature for the cat owner, but would be terrible for plants.

I'm talking about the regular absorbent kind of cat litter. The one I found is made mostly of sepiolite.

Answer 1

Sepiolite is a clay that's non-toxic (it's used in animal feed) but unlike vermiculite and perlite actually hurts, rather than helps, drainage. According to this source, it can absorb its weight in water. Unlike a hydrogel, it does not release the water back to the roots. This will leave your soil waterlogged, which will kill most houseplants.

Interestingly, sepiolite is very light, but your question (and my own experience) says that cat litter is heavy. This indicates to me that there are other components in cat litter that account for the increased weight. So, I looked into that...

According to this site (and others), non-clumping cat litter contains Fuller's earth, which is a heavy clay. According to the Encyclopedia Britannica Fuller's earth is a naturally occurring clay that is used to adsorb impurities from other materials. It turns to mud when wet, so, like sepiolite, not great for houseplant drainage. According to the Britannica, fuller's earth 'consists chiefly of hydrated aluminum silicates that contain metal ions such as magnesium, sodium, and calcium within their structure," which makes me wonder how the material would affect the fertility of the mix, especially the cation exchange complex.

Personlly, I would use a traditional bonsai mix, as i think that adding a ton of clay to the mix won't end well.

UPDATE

Additional sources on experiences with fuller's earth in pots:

• University of British Columbia blog
• Dave's Garden blog (search for "earth"; relevant text is near the bottom of the page. Note that there are said to be "mixed results" for bonsai)
• Bonsai Nut blog - an excellent discussion that you should find useful.

Answer 2

I've used it for years, but as a soil wetting agent, believe it or not for cactus and succulents. Ratios 40-50% organic, 40-50% perlite or agricultural pumice, 10-20% Fullers Earth cat litter.