Euphorbia milii: Crown of Thorns
Of the nearly 2,000 species of spurge approximately 500 are succulents (see the section on succulents). Many may be seen in botanical gardens but only one has become a house plant grown for its decorative.
Euphorbia milii (syn. E. splendens) is native to Madagascar, but nowadays may be found growing wild in practically all the subtropical and tropical countries of the world. The stem is the only succulent part of this small shrub, furnished as a defence against possible enemies not only with a poisonous milk sap, but also with long, rigid spines. The leaves are flat, oval to elongate-ovate, depending on the variety or cultivar, and only 1.5 to 7 cm (¾ to 2-3/4in) long. The whole plant is usually about 1 m (3 ft) high, but occasionally one may also encounter robust specimens up to 180 cm (6 ft) high. The flowers, like those of all spurges, are small, nondescript and borne in so-called cyathiums enclosed by two bright red bracts.
This species is definitely the easiest to grow. All that it needs is a warm sunny spot on the window-sill, the right growing medium, John Innes potting compost with extra sand added and watering in summer (any excess water that collects in the saucer should be poured off so that the roots do not rot). It is recommended to lower the heat and limit watering in winter but this is not a must as the plants successfully survive warm conditions in winter. During the growing period the plants require an occasional application of feed.
Propagation is likewise easy — by means of tip cuttings which should be immersed in tepid water to wash off the exuding milk, then left to dry for a day or two in the sun and inserted in sand. When they have put out roots they should be moved to more nourishing compost, such as the mixture already referred to.