Cotinus coggygria Seeds | Smoke Tree

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Smoke Tree (Cotinus coggygria) seed — Smoke Tree (*Cotinus coggygria*): Anacardiaceae, the sumac family; genus Cotinus holds only a handful of species, native to Dry limestone country from southern and central Europe through the Balkans, the Caucasus and Turkey to Iran, the Himalayas and northern China.

LATIN NAME: Cotinus coggygria

COMMON NAME: Smoke Tree

Plant Profile

Nothing about the cloud of purple-grey haze that appears over this shrub in high summer is a flower. The panicle carries a mass of small, greenish, five-petalled blooms, and most of them never set fruit at all; instead their stalks — the pedicels — elongate after flowering and become covered in long, feathery hairs that catch the light and blur into a soft, drifting plume. A shrub in full smoke is a shrub made of failed flowers and their hairy stems, which is a much odder piece of natural engineering than the cottage-garden name suggests, and the effect persists long after the bloom is over, because the hairs do.

Cotinus was once folded into Rhus, and the relationship is still visible in the resin canals and the milky sap of the family. The genus is small and disjunct: the Eurasian smoke tree, the American smoke tree of the Ozarks and southeastern limestone glades, and a shrubby Chinese species. Gardeners rarely meet the last two, but their existence is why lists sometimes describe the genus as having two species and sometimes three.

The species responds to hard pruning by throwing long, vigorous shoots with unusually large leaves, which is how growers produce dramatic stems for the back of a border. Cut the whole bush to a low frame in early spring every second or third year, keep it in full sun, and leaf colour in the purple cultivars is strongest on the new growth.

The purple-leaved forms are the ones most gardens grow: ‘Royal Purple’ and ‘Velvet Cloak’ both carry wine-dark foliage through the season, with smoke that reads warmer and darker than the species. ‘Grace’ is a hybrid raised at the Hillier nurseries in England, involving the American smoke tree, and it is grown for foliage colour and autumn fire rather than for the plume. Green-leaved plants, usually closer to the wild species, give the softer, hazier smoke and are worth keeping where the design calls for grey rather than purple.

Science & Biotechnology

Sumacs and their relatives are a family of pigment-makers, and this one is no exception. The heartwood carries fisetin and sulfuretin, the yellow flavone and aurone pair that made the wood a dyestuff, while leaves and sap contain butein, a chalcone that shows up across the family and is behind a good deal of its chemistry. The wood is rich in tannins as well, which is what made it useful to the leather trade.

Fisetin is widely distributed in fruit and vegetables, but the amounts used in research are extracted rather than eaten, and the heartwood of this shrub is one of the richest known plant sources. That has produced an odd situation in which an ornamental shrub has a laboratory value at least as large as its garden value, and it makes correct identification of the plant worth paying attention to.

Uses & Benefits

Before synthetic dyes, the bright yellow heartwood was traded across Europe as young fustic, used with alum mordants to dye wool and silk, and combined with iron salts to give olive and drab greens. The same wood tanned leather, and in parts of southeastern Europe it supported a village industry. Modern interest in the plant runs through fisetin instead: the compound has been studied as a senolytic agent — one that selectively clears senescent cells — in animal research, which has turned a dye plant into a raw material of pharmaceutical interest.

Growing from Seed

The species is a shrub of dry, stony, calcareous hillsides, often on rock ledges and in open oak scrub, and that origin explains its garden requirements: full sun, sharp drainage and a soil on the lean side of fertile. It is deciduous, with rounded or slightly obovate leaves that open a soft blue-green and turn to orange, scarlet and gold in autumn — the second reason it is planted. In the wild it is often cut back by grazing and by winter, so it grows as a dense, multi-stemmed bush rather than a tree.

Smoke tree seed is small and hard-coated and behaves best with a cold, moist period before sowing. Clean the dry fruits from the plumes, mix them with damp sand or vermiculite, and hold them in the refrigerator for a season; then surface-sow thinly on a mix of equal parts loam, coarse sand and leaf mould, press them in and cover with a fine layer of grit. The seed needs light and steady moisture, so water from below and keep the pan outdoors in a shaded frame. Named cultivars are propagated from cuttings instead, since they will not come true from seed.

Seedlings lift and move well at a small size and should be planted out at about knee height into a sun-baked, well-drained spot; the shrub resents being moved once it is large. Established plants may throw suckers from the roots, which can be lifted and replanted where a colony is wanted. The family’s resinous sap can irritate sensitive skin, so prune with gloves, and expect verticillium wilt to be the most serious trouble in ground that has previously carried tomatoes or other susceptible crops.

Our Take

Choose the plant for the site rather than the other way round: smoke tree wants sun and stone and sulks in rich, heavy soil. Among the family, staghorn sumac is the staghorn sumac with the same cut-leaf drama and the same suckering habit, Chinese sumac is the Asian sumac of the same limestone country, and fragrant sumac is the low, spreading relative for a dry bank. Chinese pistache is the tree-sized sumac relative I plant when the space is permanent. Cold and damp first, then a seed pan in the shade, and the plumes will come.

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