Haworthia, common name wart plant or star cactus, is not in the cactus family but rather in the lily family (Liliaceae). These succulent South African natives rarely exceed 8 inches in height. Most species are rosette-shaped, but they vary greatly in color and form. Some haworthia species feature "windowed" leaves--translucent leaves with clear openings on their tips that allow light to penetrate deep inside the plant.

Care is as follows:

• Light: Medium light is best--no direct sun, especially in summer.
• Temperature: Normal room temperature is best, except in winter, when they can be kept below 60°F. Rest period is from midwinter to late spring. Haworthia can survive temperatures down to 40°F, not lower, but prefer more warmth.
• Watering: Water moderately and thoroughly, then wait until the top half-inch dries before watering again. During rest period, only water enough to prevent the mixture from drying out completely. Do not let totally dry.
• Feeding: Do not fertilize.
• Potting and repotting: Use a porous potting mixture composed of one part coarse sand or perlite to two parts standard soil-based mixture. Since haworthias are shallow-rooted, half-pots are best suited to the clustering habit of the plants. When repotting, leave a 1½-2-inch space between the edges of the cluster and the rim of the pot to allow for new growth. Repot in spring, clean up any dead or shriveled leaves, and move the plant into a larger pot only if the rosette cluster covers the entire surface of the mixture. The largest pot size needed will be 5-6 inches. A plant that has grown beyond that size should be split up. You can also remove offsets with roots in summer to be potted up. Offsets without roots can be set out to dry (heal over) for 3 days; then press them into potting mixture and they will eventually develop roots in the mix. 

Courtesy of NYBG Plant Information Service