Cactus house plants are easy to grow and vary widely in size and shape. There are hundreds of different kinds of desert cacti, all of which are succulents. A cactus is distinguishable from other succulents by areoles, the small sunken or raised spots from which spines and flowers emerge.
Origin: Southwestern U.S., Mexico and South America
Height: Varies by species
Light: At least 2-3 hours of full sun a day.
Water: Water regularly spring through fall while plant is growing, sparingly in winter. If the plant appears shriveled and wrinkled, it's underwatered. To rehydrate it, water lightly, and then again the following day, and it will recover nicely. Be careful not to drench the soil. Cactus is likely to rot if its roots become soaking wet. Tap water is hard on cactus plants and can cause hard water stains. Use distilled or rain water and water from the bottom or water the potting mix.
Humidity: Average (around 30-40% relative humidity) to dry air.
Temperature: Average room temperatures 65-75°F/18-24°C. In winter, a cooler place to rest -- 50-60°F/10-16°C at night is ideal.
Soil: Use a potting mix that drains well. You can buy a mix specially made for cacti, or use 2 parts all-purpose potting mix with 1 part sharp sand or perlite. Adding about a 1/2-inch layer of pebbles to the bottom of the container will help drainage and also add weight to the bottom. (Large cacti can become top-heavy).
Fertilizer: Typical cactus house plant fertilizer is 2-7-7. It needs less nitrogen than foliage plants and higher phosphorus and potassium for better flowering and strong roots.
Propagation: Many cacti grow offsets at the base of the parent plant. Cut them away with a sharp knife. Allow the cut surface to dry for a couple days so it doesn't ooze sap and to prevent the new plant from rotting. Place offsets on the surface of moist, sandy potting mixture. Keep new offsets in a warm, bright place, but out of direct sun for the first month. The best season to propagate is late spring or early summer, when plants are beginning their most active period of growth.