Tree Cactus Opuntia

Prickly pear cactus is the most widespread of all genera of the cacti (Cactaceae) family. It contains 145 accepted species and occurs naturally in North and South America. It can now be found around the world due to its escape from cultivation and has been become a noxious weed in some locations. They may be grown as ornamental house plants or outdoors as shrubs in borders or mass plantings. The plant can range in size from 3 to 20 feet tall and 3 to 15 feet wide. The genus name, Opuntia, is derived from the name of a different spiny plant that was found in the town of Opus, Greece. Opuntia may also have come from the Latin word, puncti, meaning "prickled."

The plants in this genus prefer full sun and well-drained, sandy, loamy, and an acidic to slightly alkaline pH. They are heat and drought-tolerant and thrive in plant hardiness zones 3b to 11b. The pads readily root to form new plants; in some parts of the world, they have become invasive. It is resistant to damage by deer and is highly salt tolerant. Generally speaking, as a houseplant, they need well-drained soil (preferably a cactus mix) and plenty of sunshine. In order to flower, they need high light levels and cooler winter temperatures

These plants grow in irregular clumps or mounds. Their leaves are inconspicuous and quickly wither away, but the stems have pad-like sections (cladodes) resembling leaves or paddles. The pads or flattened stems and can grow 4 to 16 inches long and 9 inches wide. They are elliptical, green to bluish-gray, and can measure 3/4 inch thick. The pads have areoles that produce spines up to 3 inches long that protect the plant from predators and can inflict painful injuries. Very minute, barbed spines (glochids) are found in the areoles and cause skin irritation. For several weeks in late spring to early summer, each pad produces 2- to 3-inch-wide flowers in shades of orange, purple, red, or yellow. After the flowers fade, edible fruits are produced. The fruits are oval, fleshy, red to purple berries that measure 2 to 3 inches long.

Wear protective gloves such as rubber or leather gloves when handling this plant. The pads ("nopales") and fruits ("prickly pears" or "tuna") are edible when peeled. They may or may not have spines, but they have tiny hair-like glochids that can irritate the skin and tender membranes. Use caution when harvesting and preparing food from the prickly pear.

Plants in this genus may used as houseplants, container plants, or planted in rock gardens, or coastal and desert areas. Plants are easily propagated from cuttings. A single "pad" (flattened stem section) will root and produce a new plant.

Insects, Diseases, and Other Plant Problems:  The prickly pear cactus generally has no serious insect pests or diseases. Cochineal insects or scale insects live on the prickly pear cacti and feed on the plants moisture and nutrients which can result in the death of the plant. Symptoms of cochineal infestation include a white, splotchy mold-like substance on the cactus pads. Wet or soggy soils can result in root rot.

VIDEO Created by Laura Barth for "Houseplants, Succulents, and Cacti", a plant identification course offered in partnership with Longwood Gardens.