This mature astrophytum capricorne var. niveum is now resting as it's winter time here and temperatures are at freezing point. It does not receive water at all this time of the year and is kept in a well aerated, dry and well lit environment - sunlight only. It is a cold hardy specimen which can withstand temperatures of -10ºC, although in my set-up it rarely gets below 0ºC. In summer time it is kept in full sun at temps often above 40 ºC and flowers profusely if watered abundantly once a week or so. I use exclusively rainwater.
The soil mix is coarse comprising perlite, coco choir, small gravel, sand and self produced wormcasts. I rarely use nutrients on it - once or twice a year maybe. If so, I use something preferably organic with low N and high PK values enriched with microelements.
