Cotinus Miller

This little genus is closely related to the sumachs, Rhus and Toxicodendron, but differs obviously in its simple, rounded leaves and in its inflorescence: after flowering, the seeds are protected within a large, flimsy plume of ramifying slender sterile stalks, each covered (in most of the species) in long soft hairs. This unique structure makes it hard for small mammals and even birds to reach the seeds, and as it breaks up it allows the wind to transport the seeds away from the parent plant, or even to roll across rocky ground. With its light-trapping hairs this smoke-like plume is also pretty, and has helped to make one species, Cotinus coggygria, among the most popular of garden shrubs.

Cotinus coggygria also enjoys by far the broadest natural range within its genus, extending from the western Mediterranean to central China, although a phylogenetic study in 2023 indicated that some Chinese variants conventionally treated as C. coggygria are less closely related to other forms of C. coggygria than they are to some of the other temperate species (Liu et al. 2023). The other six taxa currently recognised by Plants of the World Online (Royal Botanic Gardens, Kew 2024) are relic plants with small and sometimes fragmented natural ranges among limestone hills – to such an extent that many gardeners will assume that C. coggygria is a stand-alone species.

In the south-eastern United States, Cotinus obovatus is the only really tree-sized member of the genus and is often considered to show the brightest autumn colours of any American tree, within a biome excelling in this feature; despite these qualities, it has lost out to C. coggygria as a garden plant even in its native range.

One of two Chinese endemic Cotinus with greatly restricted ranges and a compact habit, C. szechuanensis was introduced to Europe from north-western Sichuan by Roy Lancaster in 1993; it remains exceedingly rare in cultivation, but has contributed some of its genes for diminutive stature to the slightly more widespread hybrid C. DUSKY MAIDEN (‘Londus’).

Cotinus nanus W.W. Sm., described in 1916 from mountain slopes in north-west Yunnan, is an even more diminutive shrub, reported not to exceed a metre tall (Min & Barfod 2008). It does not seem to be in cultivation, and has been assessed as Endangered in the wild (IUCN 2024). C. kanaka (R.N.De) D.Chandra from subtropical Assam (India) was first described (as a species of Rhus) in 1942 and would probably not be hardy in our area; neither would C. chiangii (D.A.Young) Rzed. & Calderón or C. carranzae Rzed. & Calderón, described in 1977 and 1999 respectively from subtropical Mexico (Royal Botanic Gardens, Kew 2024).

Cotinus species all share an aromatic yellowish resin which permeates the wood, and was once used as a dye, and which quickly clogs a saw. Although the genus belongs within a sometimes dangerously toxic family, this resin only tends to irritate the skin of a few susceptible people. A waterproof wax also coats the foliage, becoming evident when rain or dew sits in spherical globules upon the leaves.

Genetic evidence suggests that the genus evolved in the middle Eocene epoch, radiating rapidly in the middle Miocene (Liu et al. 2023). Like so many temperate trees and shrub genera, its range has retracted over the last few million years as a response to Ice Age-related climate change.

Although Cotinus coggygria is currently among the most popular and ubiquitous of western garden plants, little attention has yet been devoted to the development of new ornamental characteristiscs by crossing it with the other species. In southern England in the late 20th century a few successful hybrids were bred, including C. ‘Grace’ (C. coggygria ‘Velvet Cloak’ × C. obovatus) and C. DUSKY MAIDEN (‘Londus’; C. coggygria ‘Velvet Cloak’ × C. szechuanensis). Below, these hybrids are listed under the general headings C. coggygria × obovatus and C. coggygria × szechuanensis.