Oaks of the World

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 Quercus coahuilensis
Author K.C.Nixon & C.H.Muller 1993 Brittonia 45: 150 1993.
Synonymshypoxantha auctores, not Trel. 1924
Local names 
RangeMexico (Coahuila, Chihuahua); 2000-3550 m;
Growth habit may sometimes reach more than 5-6 m tall; trunk to 0.25 m in diameter;
Leaves 2-6 cm long, 1-3 wide; persistent 2 years; leathery; obovate or elliptic-oblong; base cordate or rounded; apex acute or rounded, aristate; margin flat or slightly revolute, with apically 2-4 pairs of bristle-tipped teeth; yellowish green, hairless above except along veins; densely tawny tomentose below (tomentum hardly scratchable, made of fasciate, entangled hairs); 4-8 vein pairs, impressed adaxially, prominent beneath; midrib becoming often pinkish; short grey tomentose petiole, 3-6 mm long;
Flowersstaminate inflorescence 2 cm long, flowers with anthers purple-red becoming yellow; pistillate inflorescence 1-flowered, rarely 2, on a 1-4 mm long tomentose peduncle;
Fruits small acorn, most solitary; maturing in 2 years; cup with a short peduncle (3-4 mm), half-round, with smooth, thin, appressed scales ciliate at margins; cotyledons free;

Bark, twigs and

bark blackish, fissured; twig slender (1-1.5 mm in diameter) with a grey tomentum, glabrescent; small bud, ovoid, 3-4 mm long, with slightly pubescent scales ciliate at margin; 
Hardiness zone, habitathardy;
Miscellaneous -- Sub-genus Quercus, section Lobatae;
-- Closely related to Q.hypoxantha, with which it forms the "Quercus hypoxantha complex", in association with Q.hintoniorum and Q.miquihuanensis.
-- Specimens morphologically intermediate between Q.coahuilensis and Q.gravesii have been collected in the Chisos Mountains of Texas (Q.tardifolia C.H.Mull.) although Q.coahuilensis does not exist in the Chisos Mountains (but it is not far, in adjacent Coahuila, so pollen may have infiltrated Texas...).
Subspecies and