Hi TheSucculentCity I'm doing the same thing as you; moving my plants to 90% pumice . I wonder if you could share your fertilizing method?

I think the drying times that you calculated with the pumice will be detrimental only if you water the plant/pumice while it is still wet. Beyond that, I think you may be over-thinking this and over-worrying. I get 1/8" pumice from General Pumice Products here in the U.S. I just sifted and washed a bucketful over the weekend. It is drying in big oil pans outside -- and right now, it's really cold here in SW Florida. I don't think it will be fully dry until Thursday, and that will be 5 days. Chris is right -- use unglazed terra cotta pots if you can. Even with pumice, they will remain lightweight. Haworthias in pumice shouldn't need to be watered more than once a week, unless you live in hot southern Florida in the summer. Even then, mine only get watered about every 5 days. You don't HAVE TO water a Haw the very minute its mix is dry. You can wait a day or so and it will be fine.

Yes, the Gary Gragg videos. He has some beautiful trees, even though I find it a bit annoying to listen to him. I'm always thinking, "Get to the point already!" But, to your point, yes, the mounding and mulching is definitely going to happen here. Interestingly, the Japanese method mounds 60 centimeters above ground and uses a long rubber sheet that is that wide. They wrap it in a circle and tie it with some kind of nylon a bit more rugged than you would see on luggage at the airport. The soil then fills the circle and the tree is planted in there. five years in a 2-meter diameter circle, and then they expand to a wider area. We have an intense rainy season and heavy clay soil. I want to get those roots into the native soil, but I have heard some stories of the tap root getting rotted out after the trees have been in the ground for several years. I really don't want to have healthy trees for a few years only to have the rotted taproots be the reason they die. So, with that nightmare in the back of my brain, I keep coming back to digging a meter down and putting in some kind of drain to push water out and down the slope. I don't mind the rain going through the soil because I think avocados like that, but I want it to have a path to exit. Since avocados usually get a tap root of 1 meter, I figure I can dig down maybe 50 cm to install some kind of simple drainage system, cover with native soil with maybe 10 percent pumice and then build up 60 cm above ground with the same soil. I could add 25 percent pumice to the top 18 cm and heavily mulch.

iochroma, Unless you've lived in another part of the country that doesn't have pumice readily available, you know not the pain of trying to find it at all, never mind finding it at a reasonable price. GPP seems to satisfy a lot of customers with a fair product at a seemingly fair price. Unless you're volunteering to send pumice out to those of us who need access to it, GPP seems reasonable. I too remember the days of $12 for a roughly 100-liter bag of pumice in San Diego, but that was then. Unless you're in SouCal or Arizona (where most of the cheap -found-in-SouCal pumice is mined), it's a difficult medium to find. Even here in BC, with lots of dormant volcanoes and pumice mines, it's difficult to find at nurseries. I don't understand it, but there you have it.