Cactus (Cactaceae)

Members of the cactus plant family exhibit a variety of strange shapes, spines, and showy flowers. Even though today they are found around the world, all species of cacti except four tropical varieties are native to the Americas. Cactuses, like every group of living organisms, vary greatly. Some cactuses look like pincushions; others resemble starfish or even blades of grass. There are about 2,000 different species of cactuses.

Characteristics: Most cactus are stem succulents; that is, they have fleshy or succulent stems. With the exception of a few tall species and chollas (pronounced CHOY uh), cactuses have no or very little woody tissue. Cactuses native to North America never have leaves on mature growth. Tiny leaves that soon dry up, do sometimes form on the young stems of prickly pear and cholla (Opuntia). Instead, cactus spines are believed to have evolved from leaves. Most cactus cannot remove water from cold soils; therefore winter is the dormant season and summer is a time of active growth. All cactuses produce flowers. Areoles are where both spines and flowers usually originate. They are distributed in a pattern along the stems and sometimes have felt and long hairs. Again dependent on the cactus species, flowers can be white or a bright color such as yellow, orange, red, or lavender. For most cactuses, flowers are short-lived; the bloom lasts only a few days. Some flowers open only at night. In a few species, the bloom opens for a day or less before withering and falling off. The short blooming period of cactuses lessens the amount of water that evaporates through their soft petals.