Euphorbia lathyris aka Caper Spurge

Euphorbia lathyris, or caper spurge, belongs to the spurge family. Its native range runs from Central Asia to Pakistan. NC State also lists China to northern Vietnam. People have introduced it across many other parts of the world. It grows as an annual or biennial herb. Garden plants reach about 3.3–4.9 feet (1–1.5 m) tall. They spread up to 1.6 feet (0.5 m) wide.

The plant has a slim, upright shape and evergreen leaves. Its straight, fleshy stems have a blue-green, powdery surface. They release white latex when damaged. Narrow leaves grow in opposite pairs along the stems. Each pair sits across the stem from the next. Leaves reach about 0.5 feet (0.15 m) long. Their smooth, waxy blades have pale veins and plain edges. Sources describe the leaf colour as dark green or blue-green.

Small greenish-yellow flowers appear from late spring into summer. NC State gives May to June as the bloom period. The flowers lack petals and sit among pale green bracts. Each plant bears both male and female flowers. Bees and wasps visit them and carry pollen. The fruit forms a rough capsule with three lobes. Its seeds start green, then turn brown or grey. The fruit appears through summer and autumn.

Grow caper spurge in full sun and soil that drains well. It also tolerates some shade and moist soil. Clay, loam and sand all suit it. RHS lists acid, neutral and alkaline soils as suitable. Established plants can cope with drought. RHS rates its winter hardiness as H5. It suits informal beds, wildlife gardens and wildflower meadows. Deer and rabbits tend to leave it alone. Sow seed in spring; routine pruning is not needed.

Fast growth and free self-seeding can make this plant troublesome. NC State warns that it may spread and displace native plants. Remove fading flowers to reduce seed spread. RHS reports few pest or disease problems. NC State lists aphids, spider mites, root rot and powdery mildew. Claims that it drives away moles lack firm support. Despite its caper-like seeds, this is not a safe food plant. Its toxic sap can inflame skin and harm eyes. Eating plant parts can cause injury, and pets are also at risk. Wear gloves when handling it, and keep children and pets away. Past uses as a purgative or wart remedy do not establish safety.