 Although semi-desert cacti may be exposed to high light levels in the wild, they may still need some shading when subjected to the higher light levels and temperatures of a greenhouse in summer. Allowing the temperature to rise above 32°C (90°F) is not recommended. The minimum winter temperature required depends very much on the species of cactus involved. For a mixed collection, a minimum temperature of between 5°C (41°F) and 10°C (50°F) is often suggested, except for cold-sensitive genera such as Melocactus and Discocactus. Some cacti, particularly those from the high Andes, are fully frost-hardy when kept dry (e.g. Rebutia minuscula survives temperatures down to − 9°C ( 16°F) in cultivation ) and may flower better when exposed to a period of cold.
