Gardeners' World grit

[Ivan]

Don't know which part of Canada you live in ,but Lava rock 3-5mm grit would be fine

I live in Ontario and not much is readily available, except for limestone, and most important CHEAP to find. I have some red lava rock that I got from a bonsai guy but it is all 1/4". I would like much smaller, with some 1/4". Again, not easy to find. There is black and red but it is large. Mostly used as decorative stone in gardens and walkways.

..There is quite a lot of aquarium grit which I have found agreeable, even if it needs washing first!

I find aquarium grit a bit to smooth for my liking. I do have some, though. Thank-you

I use granite grit from the local quarry...

I do have some granite, I think? It comes as "Tubesand" in a long bag used as winter weight in a car/van trunk as added weight.

Granite, flint, quartz, its all pretty inert stuff. Usually depends what is available locally. Up here it is quartz. Just avoid limestone and all its variants, such as marble, chalk, or oyster shell. You can always test a small sample in vinegar, any noticeable fizzing is a bad sign...
Then make sure you choose a sharp grit. Smooth stones don't help drainage as much. Pick a size to suit your pot size, but probably 2-5mm in most cases.

quartz! quartz! quartz! That is what I want. Again I can find it in large chunks used as decorative stone. It is way too much bother to crush it down and most of it powders anyway. Interesting that you would mention marble to stay away from. I tried some of the "Tubesand" which I thought was marble in vinegar this morning and there was no bubbling. uummm? I definately prefer sharp stones to smooth for a number of reasons.

[Cactusgirl]

I buy bags of small grit/gravel from Homebase. 25kg bag for about £3 I think. My plants appear to be thriving quite well in it.

[iann]

Just as a caveat: Lithops don't much care about limestone. They certainly don't need it, but also don't seem to suffer when growing in it. Some of them are found on calcareous substrates, most aren't. Possibly they grow so slowly that the substrate makes little difference. "Limestone" for me is fairly soft builders aggregate but never more than about 20% of the total soil mix and usually a lot less; not sure how the Lithops would do if all the coarse material was limestone.

[gerald]

Smooth stones don't help drainage as much.

Is that true?

[Ivan]

Since I can get limestone in abundance and next to nothing, I think it's time I did some growing in it. I got flowers last season and now have some seeds to use, so time to experiment. Unfortunately I won't see result for years.

It is sold as Chips and Dust. It has some very fine dust that hardens almost like concrete. It is used for walkways. A bit of sifting and a thorough washing results in this. I don't think it is all limestone, though.

[FaeLLe]

Since I can get limestone in abundance and next to nothing, I think it's time I did some growing in it. I got flowers last season and now have some seeds to use, so time to experiment. Unfortunately I won't see result for years.

It is sold as Chips and Dust. It has some very fine dust that hardens almost like concrete. It is used for walkways. A bit of sifting and a thorough washing results in this. I don't think it is all limestone, though.

Limestone will mess the PH up so much your cacti / succulents will not survive for sure!

[Jim_Mercer]

Since I can get limestone in abundance and next to nothing, I think it's time I did some growing in it.

If you are going to use Limestone for everything I would suggest you add a few drops of vinegar when you water to make sure the water you use is slightly acidic

[Ivan]

Limestone is only part of the 'Dust and Chips' mix so I will have to check the PH and see. I am more interested in seeing if it continues leeching into the mix over time.

I am not planning on using it for everything. In fact, I plan on experimenting with a few cacti and mesembs seeds only at this point. Since I use only rain water, I would prefer not adjusting it. It's much easier keeping it simple for me.

[iann]

Limestone will essentially turn the soil mix alkaline until it is almost all dissolved (reacted away). There are different chemical and physical forms that react more or less quickly when less alkaline substances like water are added, but the end result is always very similar.