Family: Euphorbiaceae

This extremely large genus consists of about 2000 species of widely differing form, although the flowers of the various species are very simi­lar. In fact, they have a distinctive, very com­pact inflorescence, known as a cyathium, and the coloured part of some species, such as Euphorbia pulcherrima (poinsettia), is actually a set of bracts; the actual flower is the insignifi­cant centre. Euphorbias range in size and shape from the giant, candelabra type to small ground-hugging plants the size of tennis balls. Many form clusters of small heads and others have arms radiating from a central head. Some are confused with species of cactus. Many species are leafless; others have deciduous leaves. The seed capsules dry and pop open, dispersing the rather hard seeds far on hot days. Euphorbias are native to a range of habitats, including many parts of Africa, Madagascar, Europe, western Asia, eastern India, the Canary Islands and the Americas. All species may cause discomfort if eaten and the caustic sap can cause burning and irritation of the skin.

Species

E. candelabrum, zone 9, from South Africa and Somalia, is a tree-like, succulent shrub to 10 m (33 ft). The many branches have undulating, winged margins bearing pairs of short, sharp thorns and tiny, rudimentary leaves on the young growth.

E. caput­medusae, Medusa's head, zone 9, is a succulent from South Africa, with a thickened trunk from which radiate snake-like branches, the top half covered with deciduous, linear leaves, up to 15 mm (½ in) long. Beautiful, yellow inflorescences appear at the tips of young branches in summer.

E. characias, zone 7, from Portugal and the western Mediterranean, is an evergreen shrub-like species popular for both its foliage and inflorescences which provide highlights or contrasts. These grow to over 1 m (3 ft), with blue-gray-green leaves and lime green, long-lasting inflorescences. The subsp. wulfenii is the form most often grown.

E. fulgens, scarlet plume, zone 10, is a non-succulent shrub from Mexico, to 1 m (3 ft), with slender, pendulous branches and yellow flowers encased by small, fragrant, orange-red bracts, appearing after the willow-like foliage has fallen. Frost-sensitive, it needs a warm, sheltered position.

E. griffithii, zone 5, is an herbaceous perennial species to 90 cm (36 in), with mid to dark green, linear leaves and orange to scarlet inflorescences. Flowering lasts through summer.

E. marginata, snow on the mountain, zone 4, is a non-succulent annual, native to North America, growing to 60 cm (24 in). It has white bracts and soft leaves with white margins.

E. milli var. splendens, crown of thorns, zone 10, is a climbing or trailing plant from Madagascar. Almost leafless, it has bright scarlet bracts in spring or summer, the flowers persisting for months. This striking species is suitable as a pot plant in the home or greenhouse and may grow 1 m (3 ft) or so wide.

E. obesa is a South African succulent which forms an unbranched, brownish green sphere, 12 cm (5 in) across, with a distinctly ribbed and furrowed surface.

E. pulcherrima, zone 10, a native of Mexico, is the popular poinsettia, a familiar sight at Christmas in both hemispheres. A deciduous shrub, it grows to 3 m (10 ft) tall and nearly as wide. The long,
unbranched stems have large, ovate, pointed and toothed leaves, though it is mostly grown for its large, showy bracts appearing in autumn and lasting through winter. The inflorescences can grow to 15-30 cm (6-12 in) across. Pink, salmon, yellow and white-flowered single and double forms are available, as well as dwarf forms for pot culture.

E. tirucalli, caustic bush or pencil tree, zone 10, is a succulent, to 5 m (16 ft) tall, from eastern and southern Africa and the Arabian Peninsula. It has twiggy stems and tiny, deciduous leaves which autumn quickly. Once used to make latex, its sap is caustic and poisonous.

Cultivation

Most non-succulent species require almost frost-free conditions outdoors, though they can be grown successfully in greenhouses where necessary. They are usually grown in pots as indoor plants or for transplanting. Older specimens should be pruned back heavily after transplanting. Prune deciduous species each year after flowering, both to encourage good blooms the following season and to maintain their shape. Propagate these species from cut­tings, allowing the cut surface to dry for at least a few hours before planting. In frost-prone cli­mates, most of the succulent species are grown in a cool to intermediate greenhouse or conser­vatory. Grow them in pots of well-drained, soil-based or cactus compost. They need maximum light and airy conditions. Keep dry in winter but water normally in the growing period. Hardy herbaceous perennials and shrubs need a sunny or partially shaded spot in the garden with well-drained, fertile soil. Propagate these by division in early spring or from stem-tip cuttings.

Climate

Depends on species; some require hot, tropical conditions, others tolerate frost.