Cotinus obovatus Raf.

Cotinus obovatus has a limited and fragmented wild population, centred on the Ozark Plateau of Arkansas and Missouri, the Arkansas River in eastern Oklahoma, the Cumberland Plateau in northeastern Alabama, Tennessee, and Georgia, and the Edwards Plateau in west-central Texas (Candelas 2021). Even within these regions is it something of a niche plant, confined to rocky, calcareous soils prone to drought, and favouring north-eastern slopes and the shade offered by trees of Juniperus ashei (Lady Bird Johnson Wildflower Center 2024). This showy tree managed to elude the attention of western science until 1819 when it was noted by the English-born botanist Thomas Nuttall; in describing it however, Nuttall was pipped by a Frenchman, the polymath Constantine Rafinesque, who in his later years had settled in Ohio.

The species shares the yellowish, resinous wood of the European Cotinus coggygria, and for a few decades it was similarly exploited as a source of the dye called ‘young fustic’, until it was reprieved by the advent of synthetic dyes in the 1860s. The durable timber was also used for fence posts, whenever this came in straight enough lengths (Candelas 2021; Dirr 2009). Today, despite its limited and much fragmented range, the American Smoke Tree is assessed as a species of Least Concern (IUCN 2024).

Cotinus obovatus shares many of the ornamental qualities of its European cousin. It is more vigorous, and can become a tree reportedly as tall as 18 m. Its grey bark develops deeper fissures and the ridges can flake in the shaggy fashion of various unrelated broadleaved trees from the eastern United States, so that its pattern can even resemble giant, loose fish-scales (Dirr 2009). The flower- and seed-heads do not ramify as densely and showily as those of C. coggygria, and the individual plant is more likely to be male or female; some authorities suggest that males are showier in flower, with others preferring the female plant (whose seed-head lasts much longer). The leaves are a little bigger than those of C. coggygria, with a longer taper towards the stalk and with a typically denser cover of silky hairs underneath when they are young, and in autumn they colour even more briiliantly: many people claim that this display of orange and scarlet is the most spectacular of any American tree, and is all the more remarkable for developing over alkaline rather than acid soils. In spring, too, the foliage is glorious, flushing a delicate bronze-pink.

Partly because of its less amenable stature, the American Smoke Tree has comprehensively lost out as a garden plant to its European rival, even within its native biome. In 2024, the excellent North Carolina Extension Gardener Plant Toolbox illustrated the species’ autumn colour not with a photograph of one in America, but of the well-known old tree that stands conspicuously near the Victoria Gate at Kew Gardens in London. For the European dendrologist, used as we are to the total inferiority of our continent’s autumn colour show to that of the eastern United States, this is rather flattering; the Kew tree is thoroughly at home in the garden’s rather infertile and drought-prone gravelly soil, but the species’ display can be hit and miss in Britain, particularly when the growing conditions are too soft (Edwards & Marshall 2019; Bean 1976). Cotinus obovatus luxuriates in the rich but rather alkaline soils and the warm dry summers of the Cambridge University Botanic Garden, but a young tree at Grayswood Hill, growing on the Surrey greensand which suits most plants so well and illustrated in early autumn colour above, died rather suddenly in 2021 (The Tree Register 2024).

The old tree at Kew is a descendant of the first plants sent to Europe, by Charles Sprague Sargent in 1882 (Bean 1976); in 2022 it was 9 m × 41 cm dbh on the largest of several, fusing trunks (The Tree Register 2024), and had begun to show signs of decline. In Europe the species remains little more than a collector’s tree, although it has at least contributed its autumn colouring genes to several currently popular smokebushes (C. ‘Candy Floss’, C. ‘Flame’, C. ‘Grace’ and C. ‘Ruby Glow’), all of which flower as showily as their European parent can. The American tree’s taller stature has recommended it for street planting in a few cities, such as Portland, Oregon (Xera Plants Inc. 2024). It is also available in Australia (Teese 2024) and in New Zealand (Leafland Wholesale Tree Nursery 2024).