The large family of cacti encompasses more than 2000 plants, all of which are succulents.
It is a common misconception that spines are the characteristic that distinguishes cacti from other succulents. Although most cacti have spines, some do not. The distinguishing characteristic is the presence of areoles, the small sunken or raised spots on cactus stems from which spines, flowers, and leaves grow.
All cacti must be given soft water and demand a special potting mix (available commercially). They require few nutrients, but must be provided with special cactus fertilizer. Cacti grow in almost any kind of container. Desert cacti absolutely require a sunny location; epiphytes should be placed in a light spot with only occasional direct sun. Humid air sults none of the cacti. In the summer, normal room temperatures are fine, but during the rest period it must be cooler. The annual rest periods should be respected. Water desert cacti in the summer when the soil feels dry-but then water thoroughly. During their rest period, the plants need hardly any water. Fertilize lightly during the growing season.
Light: Provide at least 4 hours of curtain-filtered sunlight from a bright south, east or west window.
Water: During dormancy, water sparingly. At other times, water thoroughly, but allow to dry between waterings.
Humidity: Dry air is generally not harmful, but keeps plants out of drafts.
Temperatures: To set flower buds, 40° F to 45° F at night, 60° to 65° F during the day. At other times, 50° F to 55° F at night, 65° F to 70° F during the day.
Fertilization: Fertilize lightly during the spring and summer growing season with a low-nitrogen fertilizer.
Propagation: Start new plants by dividing an old specimen. Seeds are available, but can be more difficult than division.
Grooming: None usually needed.
Repotting: Repot infrequently.
Problems: Poor drainage, too frequent watering, or standing in water will cause root rot. WIll not bloom if light is too low.