Useful Facts on Cactuses

What are Cacti?

• A cactus is a type of plant known as a "succulent," meaning that it has a fleshy stem adapted for water storage. Many garden centers and nurseries will use the term "succulents" to distinguish plants like this that are not cacti but, to a botanist, a cactus is merely a type of succulent. Some succulents have leaves or adapted leaves that are puffy or spherical, but cactus do not have leaves as such; instead, they frequently have scales or spines. These spines, Deborah L. Brown explains, not only protect the plant from predators, but they also "aid the plant in withstanding hot drying rays of the sun." In addition to their fleshy stems and scales or spines, cacti also have flowers, often very colorful.

Types of Cacti

• The great variety of cacti includes tiny specimens that can sit on a windowsill as well as giants that tower much higher than a person. Shapes vary as much as size, according to Clemson University horticulturist Karen Russ and floriculturist Al Pertuit, who note that cacti can grow "as upright columns, as spreading clumps, limited only by the size of their container, as hanging baskets or as thorny ornamental balls." The type of cactus you choose, therefore, will depend very much on the available space you have and the appearance you prefer. One other distinction, however, is very important for home gardeners: arid types versus tropical. Most true cacti are those adapted for living in deserts, but the popular Christmas cactus originates in Brazil and is less drought-tolerant than its spinier cousins.

Care of Cacti

• One of the reasons cacti have become so popular as houseplants is their ease of care. Arid-climate and Christmas cacti alike "thrive on benign neglect," says Purdue horticulturist B. Rosie Lerner. In fact, the biggest problem for cactus houseplants is over-watering. Root rot and other problems can also arise from using soil that does not drain sufficiently, staying wet for too long. It is a misconception, however, that cacti must grow in sand. They benefit from nutrient-rich soil, as long as it drains properly. Brown recommends a mixture of one part potting mix and one part sand. To test your soil, moisten the mix and crumble it in your hand; if it crumbles, it will drain well, but if it stays clumped together, it contains too much clay for a cactus to thrive. If you are planting cacti outdoors, you may need to amend your soil to duplicate these conditions. As you might expect, cacti require plenty of light; if you are growing them as houseplants, be prepared to move them about, perhaps setting them outside during the warm summer months.

Choice of Cacti

• Depending on whether you garden indoors or out, and how much space you have, you may choose from dozens of readily available cultivars. Russ and Pertuit suggest some popular varieties, including the spineless "star" cactus, cultivars with the species name Astrophytum; the cylindrical "barrel" cactus, cultivars with the species name Ferocactus; and the small, readily flowering "Pincushion" cactus, cultivars with the species name Mammillaria. If you are choosing a Christmas cactus, note that this common name is actually applied to any of several varieties: Schlumbergera truncata, Schlumbergera x buckleyi, Rhipsalidopsis species and Epiphyllum species.