I like pumice as a soil amendment better than perilite. This doesn't have to do with any study about how plants grow, it is about how it feels in my fingers. Does anyone know of a cheap source of pumice? I saw in one catalog 1/3 cubic feet for about $20! Right now I am using a hammer to break up pieces collected from a family trip to Oregon many years ago when I was a child! Vicki Sironen PBS Membership Chair