How to grow Euphorbia
Named after Euphorbus, physician to King Juba of Mauritania (Euphorbiaceae). A genus of about a thousand species, widely distributed, mainly in temperate regions, showing immense diversity of form and requirements. They include annual, biennial and perennial herbaceous plants, shrubs and trees and succulent plants. The decorative parts are really bracts, often colourful, round the small and inconspicuous flowers. Some are warm greenhouse plants ; others are hardy. The succulent species are mainly from Africa, most of them from South and West Africa. Many of those resemble cacti in appearance. For the purposes of this article the succulent species are dealt with separately. All euphorbias exude a poisonous milky latex when the stems are cut, which can burn the skin and eyes and which, in some species, is poisonous if taken internally.
Greenhouse species cultivated (all non-succulent), E. fulgens (syn. E. jacquinaeflora), 2-3 feet, small leafy shrub, scarlet bracts carried on the upper side of young shoots, autumn and winter, Mexico. E. pulcherrima (syn. Poinsettia pulcherrima), poinsettia, 3-6 feet, brilliant scarlet showy bracts in winter, Mexico. The modern Ecke hybrids are increasing in popularity. They include 'Barbara Ecke', fluorescent carmine bracts; 'Pink Ecke', coral pink and 'White Ecke', white. Some have variegated foliage. Even more popular now is the Mikkelsen strain, introduced in 1964. These, with shorter stems and with bracts in scarlet, pink or white, are a good deal 'hardier' in that they will withstand lower temperatures and fluctuating temperatures, yet will retain their bracts and remain colourful for 5-6 weeks.
Hardy E. biglandulosa, 2 feet, yellow, February and March, Greece. E. cyparissias, cypress spurge, ploughman's mignonette, 1-2 feet, small narrow leaves, small greenish-yellow flowers and yellow, heart-shaped bracts, May, Europe. E. epithymoides (syn. E. polychroma), cushion spurge, 1-11 feet, rounded heads of golden‑yellow bracts, early April to late May, Europe. E. griffithii, 1A-2 feet, reddish-orange flowers and bracts, April and early May; the cultivar `Fireglow' has redder flower-heads, Himalaya. E. heterophylla, Mexican fire plant, annual poinsettia, 2 feet, scarlet bracts, annual, North and South America. E. lathyrus, caper spurge,
3 feet, large green bracts, biennial, Europe. E. marginata, snow-on-the-mountain, 2 feet, leaves banded white, bracts white, annual, North America. E. myrsinites, trailing, good when sprouting between stones of a dry wall, fleshy stems, blue-grey foliage, bright yellow flower-heads, late winter and spring, southern Europe. E. pilosa, 18 inches, usually grown in its form major, with yellow foliage, turning bronze in autumn, Europe, north Asia. E. portlandica, 9 inches, blue-green leaves, yellow bracts, British native. E. robbiae, 1 feet, rosettes of dark green leaves, bracts yellow, good ground cover plant for shade. E. sikkimensis, 2-3 feet, young shoots bright red, bracts yellow-green, summer, India. E. veneta (syn. E. wulfenii), to 4 feet, nearly 3 feet across, very handsome almost sub-shrubby plant, grey-green foliage, yellow-green flower-heads with black 'eyes', spring to summer, Europe. Other' species and varieties of hardy spurges may be found in nurserymen's cataloges.
Succulent There are very many species in cultivation: some of the following are some of the more popular ones, E. alcicornis, to 2 feet, leafless, spiny shrub, stem five-angled, Madagascar. E. bupleurifolia, dwarf, thick stem like a tight fir cone, large deciduous leaves growing from the top, pale green flowers, Cape Province. E. canariensis, shrub with small yellow flowers, many erect stems, 4-6 ribbed, short spines on edges, Canary Isles. E. caput-medusae, dwarf, thick main stem, making a large head from which radiate many thin branches a foot or more long, small yellow flowers. There is a cristate or monstrous form with thin, flattened branches, Cape Province. E. echinus, shrub with erect stem and many branches, 5-8 angled, stems similar in shape to the cactus, Cereus eburneus, south Morocco. E. obesa, one of the most popular euphorbias, plants round when young, coloured like plaid, becoming columnar, closely resembling the cactus, Astrophytum asterias; this plant does not make offsets so must be grown from seed, Cape Province. E. splendens, crown of thorns, 2-3 feet, succulent, spiny, few-leaved shrub, pairs of round scarlet bracts, mainly in spring, Madagascar.
Cultivation: Greenhouse (non-succulent) species A good compost is 4 parts of fibrous loam, I part of decayed cow manure and a half part of silver sand. Young plants should be potted into 6— or 8—inch pots in summer and kept in a cold house or frame until September. Then feed regularly with a liquid feed and bring into a temperature of 60-65°F (16-18°C) to bring the plants into flower in December. After flowering, reduce watering and temperature until the soil is quite dry. In April cut back to two buds and start to water. Repot in May when the young shoots are about 1 inch long. Pot on as required; in high summer the pots can be stood out of doors or kept in a cold frame and brought in again in September. Propagation is from cuttings of young shoots taken in summer and inserted in sand in a temperature of 70°F (21°C).
Hardy species Any good garden soil suits them. E. veneta (E. wulfenii) prefers a slightly sheltered position, but the others should be given sunny places. The dwarf kinds are suitable for the rock garden, although E. cyparissias tends to ramp, spreading by underground rhizomes. Propagation of perennial kinds is by division of the plants in spring or autumn but E. veneta (E. wulfenii) is best increased from seed or soft cuttings taken in early spring and inserted in a sandy compost out of doors or under a cloche. The annuals and the biennial, E. lathyrus, are easily raised from seed sown out of doors in April where the plants are to flower, thinning the seedlings later. E. lathyrus seeds itself freely.
Succulent species Most of these plants like a richer soil than some succulents but it must be porous. The compost should be made up from a good potting compost with a fifth part added of sharp sand, grit or broken brick. Repot in March every two years or when the plants become potbound; water well from April to September, keep fairly dry from October to March. Temperatures should be .65°F (18°C), in the growing period, 45-50°F (7-10°C) in winter. Plants should be given a light sunny place in the greenhouse or on a window sill. Propagation is by seed sown in early spring in pans of seed compost. Cover the seed with its own depth of soil, keep moist at temperature of 70°F (21°C), shade from sun but give light when seedlings appear. Large seeds should be washed well before sowing. Plants may also be propagated by cuttings which should be dusted with powdered charcoal to prevent bleeding, then dried and rooted in sharp sand and peat in equal
parts. Pot up the cuttings when they have rooted in compost.