I was at first enamored by the geometric sculptural shapes that this genus displays. From the smallest golf ball sized Astrophytum asterias to the grand golden spined Astrophytum ornatum, they are inspiring.
I realized when Brian Kemble was talking about these plants in his Mexico presentation at our last meeting that he had referenced the beautiful yellow flowers with red throats, I wanted to share and elaborate so much so that I jumped at the opportunity. OK truth be told, I backed into this but with enthusiasm nonetheless.
I have long enjoyed this genus for its relative ease of growth, it's interesting and unique forms and probably the most interesting feature ~ tremendous variation within each species. I have had the great fortune of seeing most if not all the species in the wild and that for me is a little bit like seeing your favorite music group live....you just have to be there but once you see them you become a fan for life.
So there are six “accepted” species and lots and lots of forms. These forms occur in the wild and are different but perhaps not enough so to stand alone but certainly enough to warrant ssp. or forma names so we can delineate them. More on this when I have a picture to point to. In addition to all these forms, there are a number of plants that are not of wild origin, that have come to light in horticulture and are well worthy of attention. Most notably the Onzuko types that have unusual snowflake like patterns and sometimes chevrons on the ribs that are very attractive. They are grown from seed so considerable variation occurs.
Astrophytums do hybridize and this has given rise to many cultivars to enjoy. Not all species will hybridize with other species or at least do not do so freely, But just because I could not do it does not mean it can’t be done. Even so, there does seem to be some incompatibility between some of the species.
Back to Brian’s assertion about the nice red throated yellow flowers. A. capricorne, A coahuilense and A. asterias do indeed have red throated flowers. Alternatively, the A. myriostigma and forms along with A. ornatum and the newest one of the group (formerly Digitostigma) A. caput-medusae have pure yellow flowers. Brian showed a habitat photo of Astrophytum myriostigma which should have pure yellow flowers but was at the time not in flower. Had it been, it would not have motivated me to do this plant of the month talk. Clearly there are some losers and winners here but I’ll let you be the judge.... It seems trivial ~ the interesting point is that this particular distinction has some merit in terms of hybridization. The red throated flowers cross with other red throated ones better and likewise yellow with yellow. Exceptions are of course the rule A .kraussii is a great little plant that I got seed of from Jurgen Menzel. It looks like a Astrophytum capricorne aureum but with finer spines and a pure yellow flower. A. capricornes typically have red centered flowers, this one does not..... I know nothing about its origin or if it occurs naturally in Mexico so I still have things