P. delavayi Franch.
P. forrestii W.W. Sm.
Tree to 15 m. Bark light grey-brown, with longitudinal striations. Terminal buds green, brownish in winter, to 10 cm. Leaves 20–52 cm, dark green, paler below, leaflets 7–21, elliptic or elliptic-ovate to elliptic-lanceolate, 7–21.5 × 3–6 cm, base oblique, slightly cordate to broadly cuneate, apex acute or acuminate, usually glabrous when mature except for hairs on the midrib below, axillary tufts sometimes present; petiole 5–13 cm with narrow ridges. Infructescence 50–60 cm, axis tomentose. Nutlets c. 8 mm, tomentose, wings orbicular-ovate to elliptic, 1–2.5 × 1–1.3 cm (Lu et al. 1999).
RHS Hardiness Rating: H4
var. delavayi is extremely variable, with the leaves especially varying in number, size and shape of the leaflets. It is well represented in herbaria by the collections of Forrest and Rock from Yunnan but remains scarce in cultivation, probably because it seems to be rather tender. One early collection survives at RBG Edinburgh, a 12 m (2014) specimen repropagated from F 13378 (The Tree Register 2019). A collection made by Brickell and Leslie (B&L 12575), as P. forrestii, in a wooded valley on the Cangshan above Dali, Yunnan, was distributed to various arboreta in the UK, but has died out in most. One specimen survives at Hergest Croft, and when young its new shoots were invariably killed by spring frosts, although they grew out vigorously later; in recent years, however, with increasing size, it has escaped significant damage (L. Banks pers. comm. 2006), reaching 10 m × 22 cm in 2013 (The Tree Register 2019).