Four questions about cactus watering

[mmcavall]

I read many times in the forum that cactus doesn’t like humidity, that the substrate must dry out quickly and that it must be kept completely dry between waterings and during all winter.

So here are my questions:

1) How quickly must the substrate dry out, and how much dryness it has to reach? (some possible answers would be “it must became completely dry in one day”, or “it must became dry in about 3 days, but with certain humidity is allowed to be retained until next watering”)

2) In the growing season, how many time the substrate must be kept dry between waterings (for example: “wait it dry completely after watering and then wait about 10 days before next watering”)

3) During dormancy season, cacti must receive absolutely no water for 3-4 months? Or some watering is allowed?

4) In localities were winter is not very cold, just a cool weather with sunny days, cacti must also be considered under dormancy and be treated as in question 3? Or that applies just to cacti under more severe climates?

Ok, I know there is no simple recipe and that each species has its own needs, but, in a general manner, it is possible to answer this questions?

Thanks in advance!

[mdpillet]

Your questions are very climate-dependent, as you are aware. In Arizona, I water once a week for most plants - a very good soak. (I haven't had a winter here yet since I just moved down here, but most species will likely get a good watering every 2 weeks in winter.) My standard soil mixture is about 70-80% pumice, so things don't stay moist very long. You do want your substrate to dry out, but in the growing season you don't want to wait too long either: complete drought results in root hair necrosis. Dormancy - some genera will go dormant regardless of what you do, some will not. In a subtropical/tropical clime, it's likely most species won't go truly dormant. Thus, you'll want to maintain some level of watering, but definitely not to the same extent as during the growing season. Overall - and this comes only with experience - let your plants tell you what they want. You will lose plants due to rot, and even underwatering - there's no way around it. Gradually get away from a rigid watering schedule as you feel more comfortable with interpreting your plants' health.

[iann]

1. Your definition of completely dry might need some thought. Try tipping out a pot just when you think it is completely dry, and it probably will still be slightly moist. Anyway, I'd go for completely dry in a week. It can go longer, but you don't want to start out with soil that stays wet for 10 days and end up with it being soggy after 20 days when the weather catches you out. A day is too quick, that's just teasing the plants. Cactus roots grow a bit when they have water, then dry out a bit when they don't, and it takes more than a few hours to reach peak operating speed.

2. Leave the soil dry until the plants need watering. If they are fat as beachballs and you water them, you'll just cause trouble. They might split, or they might just not take the water up and sit in wet soil. Not good either way. Water them when they need it. That might be as soon as the soil dries out, or it might be a month later. Or longer.

3. You'll have to define your dormancy season. Some cacti don't really have one, others do but it is the summer. Northern hemisphere "no watering in the winter" advice tends to come because it is cold, dull, and humid for many months. If you don't have that then you might need to water some cacti at least right through winter. Warm winters might make it difficult to grow some species, or difficult to make them flower. I'm not sure how well Pediocactus would do for you, probably be permanently dormant.

4. If they're growing then they'll need some water. Maybe not very often. If they aren't growing they probably don't need any, at least not for a month or two.

[mmcavall]

Thanks mdpillet and iann

Both replies helped a lot! I think I have a better understanding now

I noticed I was taking to much in account the "northern hemisphere advices". Totally different conditions here! I'll try to relativise things from now on.
Thanks!