Cotinus, commonly known as smoketree or smoke bush, is a genus of seven species of deciduous flowering shrubs and small trees in the family Anacardiaceae (the cashew family), order Sapindales. The genus is closely related to the sumacs (Rhus), and its species were often placed in that genus historically; they are now distinguished by their simple (not pinnate) leaves and by the dramatic smoke-like flower heads that give the genus its popular name.
Plants are large shrubs or small trees native to the warm temperate regions of the Northern Hemisphere. The leaves are alternate, simple, and oval, ranging from 3 to 13 cm in length, and turn vivid colours in autumn. The flowers are small and borne in large open terminal panicles 15–30 cm long; after flowering, the elongated sterile flower stalks develop a persistent fluffy, grayish-buff covering that gives the whole inflorescence the appearance of a billowing cloud of smoke hovering over the plant.
The genus contains two well-known species. Cotinus coggygria, the Eurasian smoketree, is the most widely cultivated, valued for its ornamental foliage and smoke-like inflorescences. Numerous cultivars have been selected, including purple- and bronze-leaved forms such as 'Royal Purple' and 'Notcutt's Variety'. Cotinus obovatus, the American smoketree, is native to the southeastern United States from Tennessee and Alabama west to Oklahoma and Texas; it grows larger than its Eurasian relative—frequently 3 to 5 metres tall—and is prized for its exceptionally bright autumn foliage. Where both species are grown in proximity they hybridise, and some garden cultivars are of hybrid origin.
Etymology
The name "smoketree" and "smoke bush" derive from the fluffy, grayish-buff elongated sterile flower stalks that persist after flowering, giving the plant the appearance of being enveloped in a cloud of smoke. The botanical name Cotinus is the classical Latin name used by Pliny for the wild olive, later applied to this genus.
Distribution
Cotinus is native to the warm temperate Northern Hemisphere. Cotinus coggygria is distributed across a broad Eurasian range, while Cotinus obovatus is endemic to the southeastern United States, occurring from Tennessee south to Alabama and west to Oklahoma and eastern Texas. Additional species occur in Mexico and Asia.
Cultivation
Smoke trees are popular ornamental garden shrubs, grown primarily for their distinctive inflorescences and, in the case of purple-leaved cultivars, for their foliage. Cultivation is best in dry, infertile soils, which promotes a compact growth habit and improves autumn colour; fertile soils encourage coarse, large growth and increase susceptibility to verticillium wilt. Plants can be coppiced in early spring to produce vigorous first-year shoots with large decorative leaves, though this prevents the characteristic "smoke" effect. Common cultivars of C. coggygria include 'Notcutt's Variety' and 'Royal Purple'.
