After my previous note on the rain shelter I posted, this caused me to revisit my approach to watering in general. I know -- we're just a few weeks away from Christmas, and I already have the next growing season in mind. However, I figured that some advice on spring and summer wouldn't hurt as I think about the coming year.
For those of you who haven't already heard this before: I live in Los Angeles about 6 miles southwest of the downtown area. For the most part our climate is temperate, with temps in the 70s during spring, then heading into the 80s for the summer. Overnight lows average about 58-65. Being close to the coast, I typically enjoy late night and early morning low clouds (aka the proverbial "June gloom"), and I've seen it hang around all day from time to time, although rarely in July. Really hot spells (upper 80s to low 90s) can sometimes happen in August all the way through to the end of September -- downtown hit 100 a couple times in early September. Otherwise, I'm thankful that I don't live in the San Fernando valley!
All of my cacti and succulents are in terra cotta pots. I use a good cactus mix from the California Cactus Center (Pasadena, CA) with an additional 20-25% pumice added in for certain cacti such as Astrophytums and Turbinicarpus ss. When I started my new collection in June, my procedure was to water every plant once a week, using enough water to drain all the way through the bottom. While this was fine for hot weather, I'm now rethinking the possibility that maybe I wasn't paying attention to overwatering in the spring.
Here's my idea, and I'd appreciate any thoughts on whether or not I have it right. Basically, when daytime temps are in the 70s watering once per week should be moderate enough that cacti aren't getting more than a few drops coming out of the drainage hole. When temps are in the 80s, I'd like to see enough water drenching down through the bottom of the pot, again once per week. If there's a real heat wave, I could go with every 4-5 days for watering. However, I keep all of my cacti under shade cloth, so because my part of L.A. gets only infrequent hot spells into the 90s, I suppose weekly waterings wouldn't hurt them any.
This is my general concept, although I'm sure it's a bit oversimplified. In the interest of full disclosure, here is my collection:
Astrophytum asterias, capricorne v. senilis, and myriostigma v. quadricostatum
Echinocereus pectinatus v. rubrispinus
Gymnocalycium ochoterenae ssp. vatteri
Mammilaria microcarpus and spinossissima
Melocactus matanzus (comes in for some warmth when overnight temps go below 45 degrees during late fall and winter)
Neoporteria (Eriosyce) nidus v. senilis
Turbinicarpus macrochele v. polaskii, schmiedickeanus (could be v. macrochele or ssp. schmiedickeanus), and pseudomacrochele ssp. lausseri
The last time I grew cacti, I was going through a divorce in 1991. When I changed living situations, I was in an apartment that had no porch or patio access, so keeping any sort of collection was simply impossible. Now the situation has changed very much for the better, and after 20 years it was so nice to build a collection again. This gives me the chance to do a much better job with my cacti, so any thoughts, recommendations, etc. would be greatly appreciated. (With the online resources that are available, maybe I won't be as in the dark about all this as I was in my younger days.)