To more specifically answer Shmuel, > Also, I know [H. vaginata] is native to an area in S Africa with > clay soils. Would one still use a loose, fast draining mix in a pot? I would say No, don't use a loose, fast draining mix in a pot. I disagree with the others who answered. I live in the desert and for clay-dwellers I use a heavy mix of fine granite silt and coarse sand. I would recommend you try what I presume is your local fine-particle desert or grassland soil. Your winters are generally of low humidity unless it's raining, right? And the bulbs will be better insulated in heavy soil during the summer. If I lived in a high-humidity summer area I might use a loose, coarse mix to try and avoid rot. But summer rot is not a problem in a dry desert. Leo Martin Phoenix Arizona USA