Cat litter and watering frequency for cacti

[Nick_G]

I grow all my cacti in a mix of cat litter (Tesco non clumping and Sanicat non clumping) and a small proportion of grit. One question I'm often asked is 'How often do you water?' the assumption being that with such a free draining mix I must water more often than with a conventional JI and grit mix. Well this year I've recorded every time I watered as follows:

I started watering here in Southend at the start of April and have now finished at the start of September. I don't heat my greenhouse and I like my plants to be a bit desiccated before the cold weather arrives in the new year. I lose hardly any plants to root rot if any at all in this mix. A very few plants just die on me every year but not from rot. I disregard pot size, all the plants of a genus get watered together. They've all grown, as in got bigger, so I don't think that I'm stressing them at all.

The Escobarias got watered just 4 times and this was probably once too often. I let them shrivel right back before watering and they plump up and double in height literally overnight after being watered.

My Lophophoras were watered 8 times and I'm happy with them, they're nice and flat and hard and well coloured.

Ariocarpus received 14 waterings and they could probably have taken a fair bit more. I'll try to up the frequency next year.

My Turbinicarpus plants were watered 7 times and this was too much. They're looking a bit bloated to me. Less next year, maybe as little as the Escobarias.

The Gymnocalyciums and Lobivias were watered 11 times and they look fine but I reckon that they could take more.

So there you are, I didn't water as often as you would think.

[iann]

The cat litter holds a lot of water (surprise, surprise!) although it tends to not look like it. It also holds a lot of air even when fairly wet. Frequency of watering probably depends more on the size of the pots, top-dressing, and especially if your pots are porous, than it does on the exact soil mix. Evaporation accounts for the majority of water usage with most potted cacti. It can be interesting to examine the soil a week or two after watering; I'm often surprised to find it still damp, although 2" pots tend to go dry very fast.

[Nick_G]

Frequency of watering probably depends more on the size of the pots, top-dressing, and especially if your pots are porous, than it does on the exact soil mix.

Sorry Ian but I can't agree with you there. I grow some Adeniums in cat litter and some in JI2 + grit and if I watered the JI potted plants as much as I do the cat litter plants they wouldn't last long. Every 3 weeks or so for the plants in the JI mix as opposed to twice a week for the plants in cat litter. Same pots, no top dressing. Yes cat litter holds a lot of water but it also dries out much quicker than conventional composts. You can hear it fizz as the air escapes from the clay when you water a pot from below.

[iann]

So you do agree with me, then. You say it holds more water, but it evaporates faster. Easy enough to stop it evaporating if you wanted to.

[gerald]

I assume you use a fertiliser as well Nick?

[Nick_G]

I assume you use a fertiliser as well Nick?

Yes, 1/4 strength but not every watering.

[ralphrmartin]

Wow. My plants are in a mix of equal parts fertilised coir, grit, JI Ericaceous compost, and they get watered once a week, and once every four days in that hot June we had. They generally look very healthy. I think many plants are opportunistic - the more water and feed given, the more they use. Bit like people really - look what happens to them when they have too much...

[MikeDom]

I try not to overwater (get it wrong from time to time) and use all mediums including pure large pumice which in a large pot holds water for quite a while but it doesn't seem to matter if you water before it is totally dry. Same with cat litter I find, the air trapped in the medium makes all the difference.

One thing always puzzles me. If cacti are adapted to live in extremely dry environments, why do we water them more frequently when it is hot and dry?

[ralphrmartin]

Not all cacti come from hot and dry environments. You might be surprised to know that Rebutia minuscula can be found in something a bit like a rainforest, with Tradescantias and Begonias, for example, growing on roadside cuttings. I've seen Rebutia heliosa growing above a stream with Gunnera in it - and Gunnera needs a lot of water for its huge leaves.

Many cacti come from places which are seasonally dry. During their growing season it can rain a lot, and that can coincide with the hot part of the year too.

[Peter]

I only water (or feed) my plants once a fortnight and sometimes I forget to do that.....

There - now I've said it.