Euphorbia Information
The genus Euphorbia is one of the largest in the world. It contains about 2000 species and they can be found growing in virtually every corner of the planet. The genus also contains many different types of plant. Apart from hardy herbaceous perennials there are hardy annuals, biennials, shrubs (the houseplant poinsettia is a 6' tender shrub from Mexico) trees and many tender cacti-like succulents from tropical climates.
Euphorbia polychroma Lacy (syn. Variegata)
The leafy perennials that we grow outside in the garden come mainly from Europe and temperate Asia. Europe has around 100 native species and about a dozen grow wild in the U.K.
There are Euphorbias suitable for most garden situations. The many glaucous leaved varieties such as E. nicaeensis and rigida like hot, sunny, well drained positions whilst E. palustris revels in damp, wet conditions. E. griffithii and its cultivars thrive on heavier clay soils and remains relatively compact, whilst E. amygdaloides prefers a humus rich soil and shade. E. robbiae will thrive in dark dry shade. The miniature E. capitulata is the perfect rockery plant and the stately E. characias is the star of the early spring border. Flowering time is from February to November, the peak month being May. The predominant colour of the bracts is lime-yellow but there are also reds and oranges. Many species are evergreen and give year round foliage interest.
Growing hardy Euphorbias is, on the whole, quite easy. As a general rule, they will be happy with well drained soil, some shelter and some sun. The colour of the bracts will be more vibrant with more sun. They will tolerate the full range of soil Ph.
The plants can be propagated by division, seed or cuttings. Species are easily grown from seed sown in early spring. Heat is not necessary but a greater germination rate will be achieved with a little bottom heat. Most cultivars can be divided in February and March, and the best time to take cuttings is from June until early September. During this period many varieties produce branching shoots from the upper part of the stems after flowering which make perfect cutting material. Most Euphorbia cuttings do not need to be closely covered as they dislike humidity. Keep the compost moist but the air dry.
All Euphorbias exude a milky white sap which can be a skin irritant and, of course, should not be ingested.