Diana Pederson (DP): What type of soil should I use?
Kenneth Quinn (KQ): All the commercial cactus mixes I have tried are worthless. I suggest making your own. Get a bag of *good* potting soil, no peat. Take one part of it, 1 of perlite (pumice if you can get it) and 2 parts of pea gravel.
If you live where cacti grow wild, you might consider getting some native soil!
DP: I find this very interesting. I grow all of my cacti/succulents in a peat based mix. Haven't had trouble with rotting but wonder if this is why some of the plants seem to just sit without growing or anything. I do know my Haworthias and Gasterias like it because they regularly flower for me. The Euphorbias seem to tolerate it too as long as I keep it on the dry side.
KQ: Just goes to show you, get ten growers together and you'll get 100 versions of best soil to use!
DP: How often should I water them?
KQ: There is not a good answer to this question, because it varies according to type of plant, the season, climate, soil, and even what type of pot! In general, water more when it is hot, and little or none when the weather is cold. If the plant is dormant, water it only if it begins to shrivel.
Terra cotta pots dry quickly, plastic pots don't. A good test, in growing season, is to stick a freshly sharpened pencil an inch or two into the soil. If the end feels or looks wet, do not water. If you are not sure a plant needs water, don't water it!
DP: Good advice Ken. I see too many houseplants including cacti or succulents killed by overwatering! Let me add that some succulents need more watering than cacti. It really upsets me when nurseries or greenhouses sell "dish gardens" with both cacti and succulents. It too often becomes a matter of which plants do you kill!
How much fertilizer and what kind should I give them?
KQ: I don't even fertilize often. When I do, I use a 10-10-10 fertlizer, greatly diluted. These are slow growing plants, they do not need heavy feeding.
DP: How can I tell how much light my plants need?
