First, let's clarify some terminology. All cacti are succulents, but not all succulents are cacti. While both cacti and succulents have thick fleshy parts that can store moisture for use when times are tough, the similarity ends there.
A true cactus has an areole. It looks like a patch of cotton from which spines, flowers, and roots grow. While some succulents may have spines, they do not have areoles.
Although some succulents are winter hardy, many are native to warmer worlds and are quite content as easy-care houseplants. All they need is a bright, sunny location, proper temperature, and occasional watering. Succulents are happy next to southern exposure windows or near fluorescent lights.
The growth cycles of cacti and succulents are usually in response to water and temperature. Most go dormant during the fall and winter when temperatures are cooler and moisture and light levels are low. They do their best growth in summer.
Even though cacti and succulents can tolerate dry conditions for extended periods, they appreciate some water, especially during their active growth period. Therefore, the soil should be watered thoroughly but allowed to dry for a few days. Be sure to use a well-drained cactus soil mix. In winter, keep dormant plants on the dry side for longer periods. Overwatering dormant succulents can lead to the rotting of the plant's stems or roots.
Dormant plants prefer temperatures between 45 and 55 degrees F. Flower buds are more likely to form at cooler temperatures. Areas next to windows often provide the perfect growing environment during the winter and satisfy the cool temperature requirement. Average room temperatures will not harm the plant, but cold helps to promote flowers.
During the summer, cacti and succulents like to be outdoors. So, locate them where they get light shade and keep them watered.
Unusual is the operative word when describing cacti and succulents. One look at the variety of sizes, textures, and colors will make a fanatic succulent collector out of many gardeners. A few succulents are good starter plants for their ease of maintenance.
The Mammillarias or Pin Cushion cacti are commonly sold. Their silky hairs give rise to names such as Bird Nest Cactus, Old Lady Cactus, and Feather Cactus. They flower readily with a halo of white to pink flowers.
One of my favorites for their architectural look is the Aeoniums. These succulents grow in flat pinwheels in colors of green, bronze, or silver.
One quick look at Lithops reveals the source of their other name – Living Stones. In contrast to other succulents, their dry dormant period is summer. However, with the proper care, daisy-like flowers may appear in November or December through "cracks in the stones."
Cacti and succulents are your perfect pet rocks if you love weird and wonderful.
- Succupedia: Browse succulents by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, Origin, or cacti by Genus