Dear All, Sorry to be so late in answering to questions! I grow Hippeatrum aulicum in an open compost made of shredded wood composted with grass clippings and horse manure. This wonderful compost is mixed with perlite and commercial potting compost.It works wonders on epiphytic cacti and also on the two epiphytic Hippeastrum species, H.calyptratum the other. I saw them in nature growin on moss covered tree trunks where the large fleshy root system formed extensive thick structured along the trunk. This compost is too fine for orchids, except terrestial ones and unfortunately tends to decompose further. Greetings from cold and frosty Germany, Uli