Cotinus coggygria Scop.

Cotinus coggygria is the only member of its genus to remain quite common in the wild across a very wide if discontinuous range. It is also the species in which the unique, wispy nature of the flower- and seed-heads is most fully developed, making it an instantly recognisable bush through the second half of the year. The resins common to the genus give the foliage an orange-peel aroma resembling that of Liquidambar and Pistacia chinensis (Jacobson 1996); the plant was used in traditional Russian medicine to treat burns (Plantura 2024) and has many potential antioxidative, antibacterial, antifungal, antiviral, anticancer, antigenotoxic, hepatoprotective and anti-inflammatory uses (Matić et al. 2015).

Smokebush was also the source of the cheap yellowish dye ‘young fustic’ (fisetin), which was economically important from the Renaissance until the advent of synthetic dyes in the 19th century, and was still used until recently in Albania. ‘Old fustic’ – which remains in use as a natural dye – derives from the New World tropical tree Maclura tinctoria; the word fustic comes from the Arabic fustug, meaning bush (Dean 2008).

Although the individual starry, yellow flowers are sparsely borne and quite inconspicuous within the developing flowerhead, Cotinus are insect-pollinated and this plant is highly attractive for bees.

This species is perhaps at its most variable in China; Min & Barfod 2008 recognise the entirely glabrous var. glaucophyllus C.Y. Yu, from Shaanxi, Sichuan and Yunnan Provinces, var. cinereus Engl. with leaves densely hairy on both sides, and var. pubescens Engl. with leaves densely hairy beneath. Plants of the World Online (Royal Botanic Gardens, Kew 2024) places these in synonymy with the type, but a 2023 phylogenetic study in China (Liu et al. 2023) has indicated that, among these varieties, var. coggygria and var. glaucophyllus seem closest to C. nanus, while var. cinereus and var. pubescens are nearer to C. szechuanensis and C. obovatus; it seems likely that these preliminary results will lead to some reorganisation within the genus. Var. pubescens and var. cinereus have also been described from Europe and west Asia (Engler 1881; Min & Barfod 2008), but it might be naive to assume that such plants are genetically very close to the Chinese specimens sampled by (Liu et al. 2023). It is perhaps unlikely that any Chinese (or Himalayan) material has contributed to the genome of today’s ornamental clones of var. coggygria.

The smoke-like flowerheads, combined with the genus’s ability to tolerate dry, infertile soils, including shallow chalk, have made this species extremely popular in western gardens. Forms from southern Europe were being grown further north by the mid-17th century, and in North America from the late 18th (Jacobson 1996); they are also adaptable enough to thrive in New Zealand and the cooler parts of Australia. The Smokebush was first named by Linnaeus in 1753 as Rhus cotinus (although kotinos in ancient Greek signified the Wild Olive); Giovanni Scopoli’s rather tricksy name Cotinus coggygria from 1771 is a mangling of the Greek word kokkygea, for this plant, meaning ‘cuckoo tree’ (Jacobson 1996; kokkygea is a feminine noun rather than an adjective, so it does not have to agree with Cotinus, a masculine Latin noun).

This is a tougher shrub than its rather southerly wild distribution might suggest, and with a bit of protection can survive a winter in USDA zone 4 (Dirr 2009). It is more likely to be tested in the cool, damp conditions of Europe’s northern Atlantic fringe: purple-leaved clones such as ‘Royal Purple’ – which are reported to be less tough than most green-leaved forms – seem apt to sicken and die in their second year in Aberdeen (Aberdeen Gardening 2024), but similar forms have made successful features in the walled garden at nearby Crathes Castle (Douglas 2022), suggesting microclimate is important. Material from Slovenia, near the northern edge of the natural European range, was introduced in 2024 to the Linnaean Garden at Uppsala in southern Sweden (Royal Botanic Garden Edinburgh 2024). Smokebushes are described as unsuitable for wet sites, but their general versatility does allow them to remain happy in quite heavy clay soils; they also tolerate acid sands, although in the wild they usually grow over limestone. Too high a fertility tends to promote growth at the expense of flowering. In general, Smokebushes suffer from few pests and diseases, and the resinous foliage is unpalatable to deer.

Despite being so easy to grow, Cotinus coggygria rarely naturalises outside its natural range. It has been reported from roadsides and waste ground in the north-eastern United States (Haines, Farnsworth & Morrison 2013), while in northern Europe it is typically considered a ‘very rare and probably always ephemeral escapee’ (Manual of the Alien Plants of Belgium 2024).

In mildly alkaline soils and given plenty of summer warmth, Cotinus coggygria is quite long-lived and can end as a low tree, with a short, nearly always slanting bole. Some of the largest trunks in England are in front of Chelmsford Cathedral in Essex (41 cm thick at 50 cm), at Stratford Park, a public park in Stroud, Gloucestershire (34 cm thick at 1 m) and in the private Pleasure Grounds of Holkham Hall in Norfolk (39 cm thick at 1 m); the first two of these belong to one of the forms with purplish rather than beige or pink flowerheads, which used to be distinguished as f. purpureus (Dup.-Jam.) Rehder. On a comparable soil in the warmest part of Ireland, a Smokebush at Kildangan Castle, Kildare was 6 m × 25 cm at 1 m in 2012 (Tree Register 2024).

In the 21st century Cotinus coggyria seems to have reached the acme of its popularity. As a garden component, it is able to engage with sunlight, rainfall and fog in ways that few plants can: dew will sit on the waxy-surfaced leaves like pearls, and enliven the naturally mist-like qualities of the seedheads like a rhinestone hairnet. As they expand, the leaves often show red and purple tints, and over the decades the selection of cultivars has largely focused on sports which retain these colours through the season. However, even the forms with the richest purple foliage will turn a variety of yellows, oranges and reds late in autumn, often showing tiger-stripes or tiny islands of different colours in between the rather conspicuous side-veins. Since the pigments in these selections with colourful summer foliage will vary with the age of each leaf and the amount of sun that it receives, and since the leaves of the wild green form have a waxy slightly bluish finish and a translucent quality, Smokebushes can become natural kaleidoscopes of different colours throughout the season, and the pigmentation even of the darkest selections never becomes as heavy and muddy as it can be in the case of many other purple-leaved plants. Although the most garishly coloured selections of plants generally seem to win out nowadays in garden centres, some of the more popular Smokebushes are among the most subtly coloured, such as ‘Old Fashioned’.

Dark purple foliage also provides a fine backdrop to the seed-heads; the yellow individual flowers are seldom at all conspicuous but these too can be foiled very effectively by the purple leaves. A smaller range of yellow-leaved clones are also in commerce; these make attractive foliage plants but the colours of the seed-head become less conspicuous and may even be felt to clash.

Another feature to have been selected in gardens is the pigmentation of the seed-head. Its many long, light-trapping hairs will always give this a silvery cast, but the colour of the stems themselves can vary within the wild population and also depends on the panicle’s maturity; they are most characteristically a creamy-yellow at flowering time then turn pink or reddish as the seeds ripen. There has inevitably been much confusion between the Purpureus Group (leaves green, seed-heads red to purple) and the Rubrifolius Group (leaves red to purple, seed-heads either yellowish or pink to purple) and in this account it has seemed best simply to list all known cultivars alphabetically – the foliage and the seed-head colours of each will differ subtly, meaning that every one could play its own part in a mixed planting. Scarcer seed-head tints include the pure ash-grey of ‘Kanari’, the salmon pink of COOKE’S PURPLE™, ‘Pink Champagne’ or ‘Westonbirt Orange’, and the soft green of ‘Green Mist’.

Since Smokebushes flower from second-year wood, coppicing them annually destroys the display of seed-heads but is recommended to create a richer show of larger, coloured leaves; Cotinus respond to pruning with very vigorous and somewhat wayward shoots, something which can count as a demerit when a bush sprawls too widely and needs to be cut back. Recently, attention has begun to focus on breeding more compact selections, suitable for today’s smaller gardens. (Another compact Cotinus is DUSKY MAIDEN (‘Londus’), bred by Peter Moore to incorporate the genes of the smaller Chinese bush C. szechuanensis.)

The UK National Collection of Cotinus coggygria is held by the Thorp Perrow Arboretum in North Yorkshire, while the Sir Harold Hillier Gardens in Hampshire maintains perhaps the world’s largest collection, not only of cultivars but of interspecific hybrids. The Royal Botanic Garden Edinburgh has a good variety of plants of known wild provenance, including collections from Albania, France, Slovenia and Turkey (Royal Botanic Garden Edinburgh 2024).