Potentially large deciduous tree to 30 m. Bark grey, fibrous, fissured when older. Terminal buds naked. Leaves imparipinnate, 20–25 cm, dark, glossy-green; petiole 2.5–5 cm, tomentose or glabrescent; rachis tomentose, not winged; leaflets (5–)7–9(–11); lateral leaflets sessile or with petiolule to 2 mm, blade elliptic-ovate to broadly lanceolate, 5–14 × 2–6 cm, pubescent on veins beneath, base oblique, broadly cuneate to subrounded, apex obtuse or acute, rarely acuminate; margins finely serrate; terminal petiolule 1–15 mm. Male spikes 8–13 cm, in clusters of 3–5, lateral on old growth, pendulous. Female spike solitary, 25–30 cm, terminal on new growth. Nutlets globose, c. 7 mm; wing a leathery disc, orbicular to ovate, 2.5–6 cm, with many fine radiating veins. Flowering time May to June, fruiting July to September (China), September to October (UK) (Bean 1976; Lu et al. 1999; Crane & DuVal 2013).
Distribution China Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, SE Yunnan, Zhejiang provinces. Taiwan
Habitat Moist mountain forests, 400-2500 m.
USDA Hardiness Zone 6-8
RHS Hardiness Rating H5
Conservation status Not evaluated (NE)
In late summer and autumn the Wheel Wingnut is unmistakeable due to its disc-winged fruits, “suggesting miniature cymbals” (Bean 1976). Rare in cultivation and hard-pressed in the wild, it is best known for its use in Chinese medicine.
The leaves of Cyclocarya paliurus make a sweet-tasting tea used in China to treat obesity and diabetes. There is a considerable body of literature documenting efforts to quantify its effects scientifically, as well as to identify active substances and their modes of action (Zhai et al. 2018). Historically, wild populations have been the source of leaves used in medicine. Fan et al. (2013) report a rapid decline in population size, and local extinction of this widely used tree. While this clearly continues, Yang et al. (2017) mention that managed plantations are becoming established.
The species became known to Western science through herbarium specimens collected in the 19th Century by the German missionary and sinologist Ernst Faber in Zhejiang, and by Augustine Henry in Hubei (Crane & DuVal 2013). Batalin’s specific epithet highlights the resemblance between the fruits and those of Christ’s Thorn (Paliurus spina-christi). Ernest Wilson collected seed in Sichuan on his first expedition for the Veitch Nursery in 1901 (Wilson (Veitch) 901) and again on later journeys. Only one tree is known to survive from early 20th Century introductions, hidden away from public view in a wood at Borde Hill, West Sussex. This was measured at 14.5 m × 30 cm in 2015 (The Tree Register 2019), giving the only indication we have of its potential size in this climate, away from the warm, wet summers of central China.
Further introductions were made in the late 20th Century through Chinese botanic gardens and by expeditions, most notably SICH 1748 from Sichuan in 1996. At Howick Hall, Northumberland, several specimens from this collection have reached heights of 5–9 m in a little under 20 years (The Tree Register 2019). Another from this collection, at the Valley Gardens, Windsor Great Park is making a fine, broad-crowned tree; viable seed is produced most years and seedlings have been raised (J. Anderson, pers. comm. 2019). However, a second nearby in the Savill Garden, grafted onto a walnut rootstock (M. Flanagan to D. Crowley, pers. comm. 2013) grew less well and seems not to have persisted. A tree at Kew, planted in 1980, was measured at 9 m × 11 cm in 2010. At Meise Botanic Garden, Belgium, there is an attractive specimen branching almost from the base, originating from Hangzhou Botanical Garden in 1991 (Meise Botanic Garden 2019). The importance of the species in the Chinese medicine trade means that other more casual seed introductions are likely to have been made. An internet search revealed multiple sources of seed for sale in China and beyond (pers. obs. 2019).
This species has barely been tested in North America. A single tree from SICH 1748 is established at Quarryhill Botanical Garden despite the summer-dry Californian climate. Bill McNamara (pers. comm. 2019) estimates its height at 7.5 m and notes that ‘we do irrigate, but it is no substitute for summer rain’. A specimen at the Arnold Arboretum, Massachusetts (25 cm dbh, 2010 - Arnold Arboretum 2019) originates from a collection made in Zhejiang in 1987 by Shanghai Botanical Garden. The Wheel Wingnut should be worth trying in the south eastern United States, but is unlikely to prove hardy in central or northern parts of North America.