Trees to 20 m tall in the wild. Branchlets slender. Terminal buds naked, golden brown. Leaves deciduous, imparipinnate, 16–30 cm long; petiole 4–9 cm, glabrous; rachis pubescent; leaflets 5–9, lateral ones sessile or subsessile, terminal one with petiolule 0.4–1 cm. Leaflets lanceolate or ovate-lanceolate, 10–18 × 2–5 cm with abundant golden peltate scales abaxially, largely glabrous except for hairs along midvein and in axils of secondary veins abaxially, bases cuneate or subrounded, apices acuminate. Staminate spikes 10–15 cm, peduncle 1–2 cm. Anthers finely pubescent. Husk winged to base; shell with 4 faint, longitudinal ridges, 1–2 mm thick, 4-chambered at base, lacunae absent. Nuts 2–3 × 1.5–2.3 cm. (Lu et al. 1999).
Distribution China Anhui, S Guizhou, Jiangxi, Zhejiang
Habitat Forests on mountain slopes, valleys and riverbanks, 400–1500 m.
USDA Hardiness Zone 6-9
RHS Hardiness Rating H4
Conservation status Not evaluated (NE)
Long grown as a nut tree in its native China, Carya cathayensis was unknown to Western science until the 20th century, and its passage into wider cultivation has not been smooth. As a wild plant it is the most easterly of the Chinese species. It remains the only East Asian hickory certainly grown in our area.
The naked, golden buds of Carya cathayensis, along with the golden scales on the undersides of its leaves, are highly distinctive. The buds superficially resemble those of C. cordiformis, whose terminal buds have yellow, leaf-like bud scales. Chinese Hickory leaves have an eye-catching bronze flush and, like other members of the Juglandaceae, are highly susceptible to damage from spring frosts (Flanagan 2015).
The species was described from material collected in Zhejiang province by the Dutch-American plant collector Frank Meyer, while working for the US Department of Agriculture in 1915. Meyer had first seen nuts at a market in Hangzhou (Flanagan 2015) and notes attached to one of his photographs show that he understood their culinary uses, including the use of the nut oil in pastry making (Meyer 1915). Though seed arrived in the United States in 1916, it is not known whether plants arose from this introduction (Flanagan 2015).
Chinese Hickory has been grown for nuts in China for at least 500 years, for most of that time in a semi-wild state. Since the 1980s, there has been a shift towards near or complete monocultures, with concomitant increases in yield (Wu et al. 2014). Development of cultivars has been slow, due in part to a high failure rate of grafts (Grauke 2003). The ability of C. cathayensis to produce seed apomictically as well as sexually (Zhang et al. 2012) may also have hampered controlled crosses, although this might in turn aid propagation. Even so, cultivars selected for yield, nut quality and early ripening are beginning to appear in China (i.e. Xia et al. 2018) and research on grafting continues.
The Chinese Hickory’s long-term hardiness outside its natural range is still an open question. While all the Asiatic species lack the bud scales, which are usually interpreted as an adaptation to cold winters (i.e. Grauke 2003), Carya cathayensis grows naturally in a climate not dissimilar to that of the north eastern United States, with hot summers and cold winters (Flanagan 2015).
Having been grown, then lost, at Kew in the 1980s (Grimshaw & Bayton 2009), C. cathayensis was reintroduced to the United Kingdom in 2015 as seed from Shanghai Botanical Garden to Kew (Flanagan 2015). Plants from this source were well distributed and are now growing well at Kew, the Savill and Valley Gardens, Windsor, Westonbirt and elsewhere. The sole plant at Westonbirt was planted at 1.6 m tall in 2016 (D. Crowley, pers. obs.), having been grown successfully in an airpot, as were all plants from this introduction (Flanagan 2015). An independent 1989 accession of wild origin seed at the Arnold Arboretum, Massachusetts, apparently came to nothing (Arnold Arboretum 2019). Like the pecan hickories, this species has proved more amenable to transplanting than the true hickories.
The following East Asian hickories are not thought to be grown in our area at present, except perhaps by the Pecan Breeding Program of the US Department of Agriculture.
Much like C. cathayensis, differing in its fruits which are distinctly obovate, larger (3–3.5 × 2.4–2.7 cm), have thicker shells (1.5–2.5 mm), and have husks which are winged only to the middle. Grauke (2003) disputes differences in leaflet number reported by Lu et al. (1999). Forests in valleys, riverbanks; 900–1000 m. Wild in valley and riverbank forest, Guangxi, Guizhou and Hunan, southern China. Also cultivated in Hunan and Guizhou. The nuts are eaten, pressed for oil and used as medicine (Lu et al. 1999; Grauke 2003).
Endemic to southwest Guizhou, differing from other East Asian hickories in that the male flowers have glabrous bracts, bracteoles and anthers, as well as its buds being almost black rather than rusty coloured (Lu et al. 1999, Grauke 2003).
The most widespread species in Asia, C. tonkinensis is found from northern Vietnam, through south east China, to eastern India. There are no reports of its being cultivated in Asia, but nut oil from wild trees is used in cooking. The hairy petiole is a diagnostic feature. The buds, rusty-brown in herbarium specimens have been described as bright orange in life (Lu et al. 1999; Grauke 2003). This species was certainly introduced to the USDA Pecan Breeding Program in 1990 (Grauke 2003).
In addition to these, C. poilanei (A. Chev.) J. Leroy is an obscure species endemic to northern Vietnam. Another, C. dabishanensis M.C. Liu & Z.J. Li, described from Anhui province, China, is more dubiously distinct. The evergreen Annamocarya sinensis (Dode) Leroy, from southwest China and northern Vietnam, is sometimes treated as Carya sinensis Dode: molecular studies (Manos & Stone 2001) give some support to this still-controversial view.