In summer, optimal growing temperatures are 25 to 35°C, and about 10°C lower at night. Most succulent plants tolerate both very high (over 40°C) and low (under 10°C) temperatures. Some can withstand light frost, while others, like Opuntia humifusa, will tolerate heavier frost.
In late fall, most succulent plants enter dormancy (in the northern hemisphere, at least). To encourage dormancy and the initiation of flower buds, cacti and agaves should be kept cool, between 6 and 12°C, while other succulents require 10 to 15°C temperatures. Dormant plants must be kept dry, in a spot with little relative humidity, because the combination of cold and damp is conducive to rot.
Succulent plants require nutrients, but in smaller amounts than most indoor plants. Fertilizer should be applied only in spring and summer, the active growing period, at two- to four-week intervals, at approximately one-quarter to one-half the dosage recommended on the label. No fertilizer is required from mid-September to March.
You can use organic or synthetic fertilizer. Leafy succulent plants, including Crassula and Aloes, require either a 20-20-20 type all-purpose fertilizer or a seaweed-based organic fertilizer (e.g. 3-7-5) alternating with fish emulsion (e.g. 5-2-2) or seaweed- and fish-based fertilizer. Fertilizers used for plants with needles or spines should be low in nitrogen but high in phosphorus and potassium. You can find fertilizers specially designed for succulents (2-7-7), but formulations like 15-15-30 (tomato food) and 15-30-15 are fine, too. Seaweed-based fertilizer is also appropriate for this type of plant. You may wish to occasionally amend the soil with calcium sulphate (gypsum) to help keep the needles and spines firm.