I love Astrophytum but have had difficulty keeping one alive more than a year (although I have two small ones in 2" pots from last summer). I thought maybe I was overwatering, so the last one I barely watered at all. It died. I got another one Tuesday and want so badly to keep it alive. It is so beautiful. Any help? I'm in the Phoenix area so I can give it all the heat and sun it wants.
Can anyone tell me what the one on the left is?