vermiculite?

[ItchyBigfoot]

Hi I've been using vermiculite in my cacti mix. Im wondering if anyone else had used mostly vermiculite in their mix. My mix is one part potting soil, one part gravel, and two parts vermiculite. I'm worried it might not drain well.

[Saxicola]

I'm not too fond of it because I think it retains water and it crushes very easily. If it works for you great! But few people use it even when making a mix for mesic (i.e. normal) plants, much less xeric ones. I've always considered it as something to be used in a seedling mix.

[DaveW]

If it works in your mix it's OK. However vermiculite tends to break down quicker than say perlite and stays wetter. Some use it in seed raising mixes for that reason since unlike mature plants cactus seeds like the soil to stay moist initially. The problem with some of these things though is they have a tendency to float when you water the plant.

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[Saxicola]

I just got looking at your picture again. What is going on with the plant right at the base where it contacts the soil? It looks like it has turned black and gone rotten. But maybe it is just the lighting of the picture. It is worth checking to make sure.

[milos]

in my opinion is better than perlite and I use it for cacti and I have no problem with water retention in the substrate

[iann]

better than perlite

Better in what respect? Smell? Cost?

[DaveW]

The potting mixes required depends on your climate or greenhouse conditions. In cold old UK we need potting mixes that dry quickly, so must be well drained and not too water retentive. If you live in a hot climate where pots dry very quickly you will need more moisture retentive mixes and vermiculite may be ideal in that case. Also soil in pots does not behave like open ground where water usually quickly sinks down to lower depths. Pots will often stay wetter longer due to the perched water table than plants near them planted in open ground, one reason we don't use soil alone straight from the garden as potting soil. Also of course whether a potting mix works for you can depend on how generous you are with watering, those who water infrequently may need more moisture retaining mixes.

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As to rain, it often buckets down in habitat since they are often watered by thunder storms, but the top layers of open ground usually drain quickly unless they are on some kind of hard pan or overlying rocks.

Mind you it used to amuse me all the old gardeners saying you should leave water standing in a can in the greenhouse to warm up before watering cacti to avoid them suffering thermal shock. If you read the reports of people collecting in habitat one moment they are sweating under hot sun and the next there was a thunderstorm and they are soaked to the skin with icy cold rain and shivering, but within half an hour or so sweating again under blazing sun, so our plants are used to thermal shocks of that kind, therefore I have never had any problems with watering cacti in full sun with cold water.

[cactushobbyman]

I have recently started to use more plastic pots due to space and price and have found my mix needs to be changed. I was using clay, now my pot are wetter longer and have had a few plants rot. Maybe since my shelf space is getting tighter, less air movement around the pots, this also is not letting the soil dry quicker.