Euphorbia characias wulfenii

Position and soil. The RHS, a British reference, gives full sun and a light, well-drained soil, chalk, loam or sand, acid to alkaline; the Missouri Plant Finder, an American one, allows part shade and says the plant needs sharply drained soil and dislikes heavy clay. Both American references read warn that wet soil in winter can be fatal or cause problems. Missouri finds it happiest in a Mediterranean-type climate and says hot, humid summers can stress it.

Water. Dry to medium, by Missouri, which finds its drought tolerance generally good but says it welcomes some moisture in dry summer periods. No Australian reference read gives a drought or frost rating for it.

Pruning. Each stem generally lives two years, flowering in its second, by HortFlora and the North Carolina toolbox, and Missouri says plants often decline after flowering. The RHS says to cut the flowered shoots back to the ground in late summer or autumn, and Missouri to cut them at the base after flowering to give the new stems room.

Propagation. The RHS gives division in early spring or basal cuttings in spring or early summer, the cuts dipped in charcoal or lukewarm water to stop bleeding; the North Carolina toolbox has stem cuttings left to dry for a few days before planting.

Pests. The RHS, writing for Britain, finds it may be prone to aphids and generally free of disease, and Missouri knows no serious problems.

The overseas references give it to beds and borders (Missouri), to Mediterranean, architectural, cottage, courtyard and wildlife plantings (the RHS), and as a specimen or ground cover on dry, sunny banks with poor soil where upkeep is hard (the North Carolina toolbox, writing of the species). The RHS lists it among its plants for pollinators. No reference read gives a planting distance; the spread runs from 0.45 m by Missouri to 1.5 m by the RHS.

Growers list this plant as Euphorbia characias wulfenii and, under the species, named forms such as Glacier Blue, Silver Swan and Tasmanian Tiger, so read the full name before comparing prices. HortFlora separates the two cultivated subspecies by height and glands: subsp. characias has stems under 0.8 m and dark reddish-brown, notched or short-horned glands, wulfenii stems to 1.8 m and yellow, long-horned glands. The table above shows the sizes growers list, and the guide to nursery plant quality sets out what to check before stock leaves the grower. Stock crossing a state border moves under the state and territory biosecurity rules on moving plants and soil.

HortFlora says the white latex of euphorbias is poisonous if swallowed and can irritate the skin. The RHS calls this subspecies an irritant to skin and eyes, harmful if eaten, and advises gloves and protective gear when handling it; the North Carolina toolbox says the sap of the species can damage the cornea and cause dermatitis.