Picrasma quassioides (D. Don) Bennett

Anyone whose repertoire of techniques for identifying trees extends to scraping and nibbling at them – as it really should – will discover that Picrasma quassioides is a ‘singularly bitter’ plant (Bean 1976). It was first described from the Himalaya in 1825 (as Nima quassioides) by Francis Buchanan-Hamilton, who compared its bark to that of the South American quinine substitute Quassia amara, a tree which was itself named after the freed Surinamese slave Quassi who discovered its medicinal use. Considerable interest continues to surround the medicinal properties of the quassinoids in Picrasma quassioides, as anti-cancer drugs (Gong et al. 2020), for their antibacterial and insecticidal properties, and as a flavouring (Wikipedia 2024), and even as a hop substitute in beer making (North Carolina Extension Gardener Plant Toolbox 2024); several western skincare products advertise the quassinoids from P. quassioides among their ingredients. The timber is attractive, with a white sapwood and a fine-grained bright yellow heartwood, and is used in the manufacture of small utensils (Fern 2024).

The tree itself is often pretty too: never tall and often multistemmed, with richly coloured reddish twigs punctuated by whitish lenticels and leaf-scars. The leaflets are broader than in most trees with compound leaves, sometimes almost round but with a long, elegant tip, and their rich green can set off the sometimes bright red common stalks. The stalks of the flowerhead can also be crimson, and female trees carry small berries which ripen through crimson to metallic blue-black. In the right conditions, autumn colour can be among the richest of any east Asian tree, ranging from gold to scarlet.

The species was introduced to Kew from Japan in 1890; both male and female trees grew together, producing fertile seed (Bean 1976), although W.J. Bean found ‘no beauty’ in the fruit of this provenance. Information on any subsequent reintroductions from the wild are remarkably scant; Laurence Hatch (Hatch 2024) remarks on the similarities shared by plants cultivated in Europe and the United States, which typically have many thin branches all rising at an angle of 45° from a very short bole – something which might suggest that they derive from a limited gene pool. The Dawes Arboretum in Ohio grows material collected in South Korea (Dawes Arboretum 2024), while a plant from Chollipo Arboretum in the same country was accessioned at Wakehurst Place, UK in 1994; two trees from WAHO 490 (Japan), accessioned in 1988, are now thriving at Kew (Tree Register 2024).

Picrasma quassioides is however a tree with an unusually wide natural distribution, and there is likely to be considerable genetic variation across this range. Peng & Wayt Thomas 2008 distinguish var. glabrescens Pamp., a less hairy high altitude form from Hubei and Yunnan in China, although few other authorities recognise this variant (Royal Botanic Gardens, Kew 2024). Jacobson (1996) reports a maximum stature in the wild of 20 m, considerably more than the western cultivated stock seems able to reach. After his extensive travels in China, Korea, Japan and Taiwan, E.H. Wilson remarked ‘although it varies slightly in degree of pubesence it is otherwise remarkably constant in its characters’ (Wilson in Sargent 1916).

The Japanese plants introduced to Kew are also likely to be much hardier than those from Sri Lanka or from the subtropical south of China; there are some remarkable disparities in the hardiness estimated by different sources for this plant. A small tree photographed in 2007 the Morton Arboretum in Illinois (North American hardiness zone 5) might offer the best evidence for its cold tolerance, but perhaps significantly the species no longer held a place in that collection’s onine catalogue by 2024. Meanwhile another specimen has grown in near identical fashion in the warm temperate conditions of Melbourne, Australia, where the blue-greens of Eucalyptus foliage serve as a fine foil for a fiery autumn colour show.

The cultivated stock in the UK certainly seems at home across the gamut of that nation’s microclimates. The largest – with short single trunks up to 35 cm thick – grow at Batsford Arboretum, Cambridge University Botanic Garden and Westonbirt National Arboretum, all sites with rather warm summers and with somewhat alkaline soils; autumn colour should however be better in a lower pH. Tallest known here is a 1987 accession, drawn up to 11.8 m in a densely planted and shaded part of the garden of Hergest Croft, Herefordshire. Slightly smaller but happy trees can be encountered in the private gardens of Lochinch Castle in the far south-west of Scotland and at Plas Penglais on Wales’s west coast, where summers are generally cool and wet. The oldest from this selection, the tree at Batsford, was only planted in 1969, suggesting a limited lifespan in Britain (Tree Register 2024).

Although it is a pretty tree, and one whose stature might recommend it for the smaller garden, Picrasma quassioides remains largely confined to big collections. There is a good example at the Mount Auburn Cemetery in Massachusetts, the world’s foremost example of a public cemetery doubling as an arboretum, and another in one more recent imitation, the Canterbury City Cemetery in England. In 1979 a substantial specimen was also recorded at Worthing Crematorium, on the highly reactive chalk of the South Downs, but this crematorium had been developed within the pleasure gardens of the private Muntham Court. In 2021 a thriving sapling pleasantly surprised the author in a piece of municipal grass in Chichester, West Sussex, where it had been added at the suggestion of the chair of the local residents’ association, who had retired from a career in horticulture (Tree Register 2024).

Good trees in the more continental climate of mainland Europe include one at the München-Nymphenburg botanical garden in Germany in 2009, and one at the Utrecht botanic gardens in the Netherlands in 2018.

The odd record of much larger Picrasma in Britain in the mid 20th century are best explained by confusion with the closely related but more vigorous Ailanthus altissima. Trees with compound leaves and heads of berry-like fruit, which may also be found mislabelled as Picrasma quassioides, include Phellodendron amurense and Tetradium daniellii – both of which differ in their bark and the opposite arrangement of their buds (Tree Register 2024).

In 2024, Picrasma quassioides was offered commercially by several UK nurseries (Royal Horticultural Society 2024), and also in Australia (Teese 2024).