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Tree to 30 m, trunk straight, erect, stately, 1 m dbh. Bark scaly, greyish or reddish brown, breaking into plates separated by longitudinal fissures. Crown dense, forming a dome. Branchlets reddish brown, thick; vegetative buds not resinous. Leaves in fascicles of three or sometimes in pairs, not or slightly pendulous, greyish green or bright green, triangular in cross-section, 10–30 × 0.12 cm, apex acute. Fascicle sheaths persistent. Cataphylls dark brown to black, gradually eroding. Male strobili yellowish to yellowish brown, ovoid, 1.5 × 0.5 cm. Female cones lateral, in whorls of two to five, with short, stout peduncles; cones 5–10 cm long, green then yellow-brown to chestnut-brown, mature cones ovoid-conical, mature in about 20 months, opening in the following summer. Scales 3 × 1.5 cm, oblong-ellipsoid, hard, stiff, woody; apophysis swollen, rounded; umbo dorsal, slightly sunken or slightly protruding, with a minute prickle. Seeds brown, 5–6 mm; wings 1.2–1.4 cm long. Fu et al. 1999c, Farjon 2005a. Distribution CHINA: eastern Guangxi, eastern Guizhou, southern Sichuan, Yunnan. Habitat Mountains, high plateaus, river valleys, between 400 and 3100 m asl. USDA Hardiness Zone 9. Conservation status Lower Risk. Illustration Fu et al. 1999c, Farjon 2005a; NTix, NT629. Cross-references B246, S381, K248. Taxonomic note Var. tenuifolia from river valleys in Guangxi and Guizhou, placed in synonymy by Farjon (2001), has pendulous leaves less than 0.1 cm wide.
Although it was introduced by Wilson, Pinus yunnanensis did not achieve wide cultivation until recently and was given only cursory treatment by Bean (1976b). It may not be the most spectacular pine in the world, but its frequent reintroductions in recent years are grounds for it receiving a fuller treatment here. The three old trees of P. yunnanensis surviving at Kew are from Wilson’s collections in Sichuan in November 1908 (Wilson 1396, 1399), sent from the Arnold Arboretum (where no examples of this species are currently grown). They have made good, though relatively short trees of 15–17 m, with dense crowns containing many long-persistent cones. The bark is thick and dark, though the ridges are reddish. A grafted young tree from Wilson 1399 grows with them. As noted above, recent reintroductions have been numerous; the 2001 catalogue of the Royal Botanic Garden Edinburgh lists accessions from six different sources, from the Sino-British Cangshan Expedition, 1981 (SBEC 109, 1043) through to Jennifer Bute’s gathering (no. 16) in 1997. The species seems to do well in most parts of the British Isles, and is grown in a few collections in continental Europe. In North America it is found in West Coast arboreta and nurseries, but seems to be absent from collections further east.