Euphorbia mammillaris aka Corncob Cactus

Euphorbia mammillaris is a succulent in the spurge family. It comes from the southern Cape region of South Africa. Its native climate is subtropical. The name corn cob plant refers to its ribbed stems. Though it looks like a cactus, it is a spurge. This long-lived perennial forms upright stems and spreading branches. Garden plants can reach 1 foot [0.3 metres] or more. New shoots grow from the base when space and light allow.

The thick stems range from grey-green to chalky green. Each stem has seven to seventeen ribs with corky ridges. Scattered, blunt spines stand out from the stems. The side branches have a club-like shape. Small green leaves appear but soon fall away. Each leaf reaches about a quarter-inch long. The stems, rather than the leaves, give the plant its form. It suits pots, patios, rock gardens, and dry borders. Deer and rabbits tend to leave it alone.

Small flower clusters form at the stem tips. Bloom can run from late winter into early summer. The source lists yellow blooms and also describes orange or pink tones. Fused bracts form a small cup around the true flowers. Each cup holds several male flowers and one female flower. The blooms measure less than an inch across. The fruit has rounded lobes and almost no stalk. It reaches about a quarter-inch across.

Give this plant full sun and soil that drains well. It also tolerates some shade during the day. Indoors, it needs plenty of bright light. Use a cactus or succulent mix in pots with drain holes. Let the mix dry between drinks. Water less in winter than during summer growth. It tolerates drought and dry soil once established. It grows in sandy or loamy soil across a broad pH range. North Carolina State lists USDA zones 9 through 11. Growers can use stem cuttings in spring or summer.

Watch for mealybugs, spider mites, and powdery mildew. Wet soil and poor drainage can cause root rot. Strong wind can wound stems and leave lasting scars. All parts contain a white latex sap with toxic compounds. The sap can cause skin rashes and serious eye injury. Eating plant parts can blister the lips and mouth. Do not treat this plant as food. Keep it away from children, cats, and dogs. Wear gloves when handling it to limit sap contact.