Thanks for this very useful article. I grow semperviums in an upside down old wide metal lampshade that I had in my kitchen some years ago. I haven't put any gravel between the plants but I'm sure it gives much better draining. I have very fine light pumice that i mix with potting soil. It drains very well. I think that might very well be used instead of fine gravel, so I thing I shoult try it. Thanks
