The Different Varieties of Cacti and Succulents

Cacti

• The plant family Cactaceae is native to North and South America and contains around 2,500 species. Plants have no true leaves but are succulent stems shaped like paddles, barrels, columns, globes and rods. Most have spine clusters emerging from growth points called areoles spaced along the stems, and the spines are thought to be modified leaves. Cacti are grown around the world as container plants. Many cacti grow outdoors in U.S. Department of Agriculture plant hardiness zones 8 through 11, but there are some that survive outdoors in USDA zones 2 and 3. Some commonly grown cacti are hedgehogs (Echinocereus spp.), pincushions (Mammillaria spp.), barrels (Ferocactus spp. and Echinocactus spp.), prickly pears (Opuntia spp.), orchid cactus (Epiphyllum spp.) and crown cactus (Rebutia spp.), spanning USDA zones 7 through 12 with variation depending on the species.

Crassula Family

• The Crassulaceae contain about 1,400 species of succulent plants, coming primarily from Africa, Mexico and the American Southwest. They store water in leaves and stems, with leaves usually displaying bright colors in response to winter sunshine. Most shrubby African crassula family members, such as jade plant (Crassula ovata) and Flaming Katie (Kalanchoe blossfeldiana), are hardy in USDA zones 10 through 11. North American rosette-forming members are more cold-hardy, with echeveria (Echeveria spp.) usually hardy within USDA zones 9 through 11. Hen and chicks (Sempervivum spp.) are hardy from USDA zones 4 through 9.

Euphorbia Family

• Succulent euphorbias are often mistaken by the uninitiated to be cacti, because many of them have fierce spinelike armament and stout columnar or cylindrical stem growth. However, the flower structure in euphorbia is completely different from cacti, and euphorbias have true leaves. The more than 1,600 species of succulent euphorbias come from Africa and Madagascar. They have milky, toxic sap, and nearly all are unable to withstand freezing weather; they are hardy in USDA zones 9,10 and 11, depending on the species. Grown as houseplants around the world, some commonly grown euphorbias are crown of thorns (Euphorbia milii) and African milk tree (Euphorbia trigona), both hardy in USDA zones 10 and 11.

Other Succulents

• The milkweed family contains succulent vines called wax plants (Hoya spp.). Stem succulents in this family include carrion flower (Stapelia spp.), with star-shaped, fly-pollinated flowers. Hardiness zones for both groups of plants are generally USDA zones 10 and 11, but some species are hardy in zone 9. Desert rose (Adenium obesum) has an enlarged water-storing caudex and stem and showy red, pink and white flowers. It is in the oleander family and grows in USDA zones 11 through 12. There are succulent members of the daisy family, melon family, agave family, lily family, ice plant family, bean family, fig family, grape family and more.