Kinds of Cactus

Columnar

• Columnar cacti have cylindrical, vertically ribbed stems that grow up to 50 feet tall, and the ribs expand when the cactus stores water in its stem. A columnar cactus stem can be more than 10 times as tall as its width, and flowers grow at the ends of the stems and branches. A well-known columnar cactus is the saguaro cactus, which grows in Arizona and Mexico. A saguaro cactus, which can live for 175 years, has a single stem with branches that appear when the cactus is at least 50 years old. Young saguaro cacti, which grow as little as 1 inch a year, can be grown in a container.

Shorter Cylindrical

• Some cacti have short, stout, cylindrical shapes: a barrel cactus, for example, measures more than 5 inches wide and grows less than 10 times as tall as its width. Spines grow in rows along the vertical stem ribs, and flowers grow at the end of the stem. A hedgehog cactus has a ribbed stem that grows up to 12 inches tall and measures less than 5 inches across. Pincushion cacti, which have hooked spines, grow in clumps near larger types of cacti, such as saguaro. Pincushion cactus stems grow up to 6 inches tall and lack ribs. Flowers emerge in a variety of colors along the sides of hedgehog and pincushion stems.

Segmented

• Prickly pear and cholla cacti have jointed, segmented stems. New segments grow from the previous year's segments, and each segment stops growing after one season. These cacti have fine, barbed spines or glochids that irritate and attach to skin. Prickly pear cacti grow up to 5 feet tall and have thick, flat segments and yellow or orange flowers. Their pads and purplish fruits are edible. Cholla cacti, also called tree cacti, have a shrubby appearance and grow up to 8 feet tall, and spines cover the inch-wide, segmented branches. Cholla and prickly pear cacti can reproduce from segments that have fallen to the ground.

Holiday Cacti

• Christmas cactus, Thanksgiving cactus and Easter cactus naturally grow in rain forests and require more moisture than many other cacti. These cacti are popular as house plants and holiday gifts, and their spineless, flat, segmented stems produce colorful, showy flowers. Holiday cacti prefer moist soil, filtered light and 50 percent humidity, but don't tolerate soaked soil. For winter flower production, Thanksgiving and Christmas cacti require reduced watering and 12 hours of darkness each day during fall. Easter cacti require similar conditions during winter to produce flowers in spring.