Science Fair Project Encyclopedia
Smoketree (Cotinus) is a genus of two species of flowering plants in the Anacardiaceae, closely related to the sumacs (Rhus). They are large shrubs or small trees, native to the warm temperate Northern Hemisphere. The leaves are deciduous, alternate, simple oval shape, 3-13 cm long. The flowers are clustered in a large open terminal panicles 15-30 cm long with a fluffy grayish-buff appearance resembling a cloud of smoke over the plant, from which the name derives. The fruit is a small drupe with a single seed. Often classified in Rhus in the past, they are distinguished by the leaves being simple (not pinnate) and the 'smoke-like' fluffy flower heads.
The Eurasian Smoketree (Cotinus coggygria, syn. Rhus cotinus) is native from southern Europe, east across central Asia and the Himalaya to northern China. It is a multiple-branching shrub growing to 5-7 m tall with an open, spreading, irregular habit, only rarely forming a small tree. The leaves are 3-8 cm long. Autumn colour can be strikingly varied, from peach and yellow to scarlet.
The American Smoketree (Cotinus obovatus, syn. Rhus cotinoides) is native to the southeastern United States, from Tennessee south to Alabama and west to eastern Texas. It is a larger plant, frequently becoming a small tree up to 10-12 m tall and with a trunk up to 25 cm diameter. The leaves are also larger, 6-13 cm long; it also has varied but very bright fall color, usually brighter than the Eurasian species. The flower heads are usually sparser than in C. coggygria.
Cultivation and uses
The smoketrees, particularly C. coggygria, are popular garden shrubs. Several bronze or purple-leaved cultivars of C. coggygria have been selected, with warm pink inflorescences set against purple-black foliage; the commonest in commerce are 'Notcutt's Variety' and 'Royal Purple'. When brought into cultivation together, the two species will form hybrids; some garden cultivars are of this parentage.
Cultivation is best in dry, infertile soils, which keeps the growth habit more compact and also improves the autumn colour; when planted in fertile soil, they become large, coarse and also tend to be short-lived, succumbing to verticillium wilt disease. Both species can be coppiced in early spring, to produce first-year shoots up to 2 m tall with large handsome leaves, but no "smoke".
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