P. insignis Rehder & E.H. Wilson
Tree to 25 m, spreading to 16 m (SICH 1751), to 3 m dbh (W.P. Fang 2721, from Emei Shan). Bark grey, fissured. Terminal buds yellow-green. Leaves (20–)30–45 cm, mid-green, densely pubescent; leaflets (5–)7–13, ovate to elongate-elliptic, 14–29 × 4–6 cm, base oblique, rounded, apex acuminate, glabrous except for veins and axillary tufts below; petiole 2–6 cm. Infructescence to 70 cm, axis glabrous or nearly so. Nutlets c. 8 mm, glabrous, wings orbicular-ovate, 1.5(–2) × 2(–2.5) cm (Lu et al. 1999; Rix 2007).
RHS Hardiness Rating: H5
Pterocarya insignis, as it was then called, was first collected in 1908 by Wilson, from a single tree on the Wa-Shan, Sichuan, as W 3212 (Sargent 1917; Rix 2007), but no living specimens from early collections have been traced. Several collections of var. insignis have been made more recently in Sichuan including SICH 1468, 1751, 2156 and most notably 1205. Material from these is now well established in cultivation (Rix 2007; Foster 2019). From these trees it is clear that this taxon is quite variable, and the character of petiole length is seen to be somewhat unreliable. One specimen of SICH 1205 planted at Kew in 1995 (1995-636) has ‘authentic’ short petioles, but another (1995-2284) has petioles up to 14 cm long (Grimshaw & Bayton 2009).
This variety is proving to be a fast growing and adaptable tree in Britain. Foster (2019) notes that individuals from SICH 1205, planted around the same time at Kew, Wakehurst, Howick Hall and Thenford House, Northamptonshire, have grown at similar rates despite significant differences in climate and soils (heights 10–11 m in 2019, The Tree Register 2019). Moreover, Foster mentions an 11 m tree in his own Kent garden continuing to grow well during the drought of 2018, despite being in a light, stony soil. This species, in all its varieties, is little tested in North America. However, specimens from SICH 1205 are recorded at both the David C. Lam Asian Garden, Vancouver (University of British Columbia 2019) and Quarryhill Botanical Garden, California (Rix 2007).
Spectacular infructescences, lack of suckers and ability to cope with diverse conditions make this an ornamental tree of great potential, which is beginning to receive attention in the wider gardening literature (Foster 2019; Sutton 2019).