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Tree to 35 m, trunk erect, sometimes forked, 0.2–0.85 m dbh. Bark scaly, flaking, reddish to greyish brown; in older trees, very thick, rough, dark greyish brown, breaking into scaly plates divided by deep, longitudinal fissures. Crown open and rounded or flat-topped. Branchlets glaucous, reddish brown to grey, scaly; vegetative buds not or slightly resinous. Leaves in fascicles of (four to) five (to six) (four more often than six), persisting for two to three years, light yellow-green to glaucous, straight, triangular in cross-section, (6–)8–15(–17) × 0.05–0.09 cm, apex acute. Fascicle sheaths 1.2–2 cm long, deciduous, so that mature leaves appear to have no fascicle sheath – an important identification character. Cataphylls small, light orange-brown, Male strobili yellowish pink then light brown. Female cones subterminal, solitary or in whorls of two to five; peduncles slender or stout, 1–2.5 cm long. Cones (4–)5–7(–8) × (3–)4–5.5 cm, pink to purplish green or purplish brown, mature in about 30–32 months; mature cones narrowly ovoid-conical, symmetrical. Scales 50–70, opening gradually; scales oblong; apophysis greyish brown, with a prominent band around the umbo; umbo dorsal, with a blunt prickle. Seeds dark greyish brown to black with black spots; seed wings effective, 1–1.8 × 0.4–0.8 cm, yellowish brown, translucent. The tree can produce adventitious shoots from stumps or the trunk, allowing it to survive fires or limited coppicing. Farjon & Styles 1997, Farjon et al. 1997, Farjon 2005a. Distribution MEXICO: western Chihuahua, Durango, Guerrero, Hidalgo, Jalisco, México, Michoacán, Morelos, Nayarit, Oaxaca, Puebla, northeast Sonora, Tlaxcala, Veracruz, Zacatecas. Habitat Montane pine and pine-oak forest between 1500 and 3300 m asl. USDA Hardiness Zone 9–10. Conservation status Lower Risk. Illustration Farjon & Styles 1997, Farjon 2005a. Cross-reference K221.
Pinus leiophylla is rare in cultivation, and even when it is grown, is usually not identified to subspecific level. An early introduction, Gardner & Knees 5318, collected in México state in 1992, must be subsp. leiophylla. Only one example of the species is recorded by TROBI, an 8 m tree at Quinta Arboretum, Cheshire, measured in 2004 by Owen Johnson, but there are trees at Bedgebury also. Recently planted seedlings at Tregrehan were killed in the winter of 1996, when the temperature there reached –6 °C, but this was ‘not a fair test’ (T. Hudson, pers. comm. 2007). In the United States, subsp. chihuahuana may be used in the southwest in plantings of native trees, but the species is seldom grown in collections in our area, although there are two trees at Berkeley, of Jalisco origin. It has bright green to yellow-green foliage, less sombre and heavy-set than most other western American pines, making a fine tree but without great beauty for horticultural purposes. In overall appearance it is surprisingly similar (particularly subsp. chihuahuana) to the distantly related Mediterranean P. halepensis (M. Frankis, pers. comm. 2007).