Oaks of the World

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 Quercus canbyi
Author Trel. 1924 Mem. Natl. Acad. Sci. 20: 188 1924.
Diagnosis here
Synonyms alamarensis C.H.Mull. 1936 Diagnosis here
graciliformis C.H.Mull 1934
graciliformis f. parvilobata (C.H.Mull.) C.H.Mull. 1940
graciliformis var. parvilobata C.H.Mull. 1934
graciliramis C.H.Mull. 1936 (A.Camus n° 393) Diagnosis here
karwinskii Trel. 1924
Local nameschisos oak; slender oak; canby oak; graceful oak;
Range Mexico (Coahuila, Nuevo Leon, Tamaulipas); Texas (Chisos Mountains ) ; from 0 to 2100 m in rocky canyons ; restricted area;
Growth habit4-15 m tall, with trunk 20-50 cm in diameter; long flexible branches somewhat drooping;
Leaves 6-10 x 2-4 cm; semi-evergreen or lately deciduous; thick, subleathery; lanceolate to narrowly ovate; apex pointed, attenuate, bristle-tipped; base acute, attenuate or cuneate; margin thick, flat or slightly revolute, with 5-6 pairs of bristle-tipped, short teeth (from base to apex, or only on the apical 2/3) with shallow sinuses, or sometimes entire; dark shiny green above, hairless or sometimes with shorts stellate hairs, and glandular hairs mostly along veins; dull, yellowish-green beneath, glabrous or with axil tufts; 5-7 vein pairs, mostly straight; epidermis slightly papillose ; petiole hairless, slender, flexible, 1-2 cm long;
Flowers April-May; male catkins pubescent, 3-5 cm long, with 20-30 flowers with 5-6 stamens and glabrous anthers; pistillate ones 0.5-1 cm long, 1 or 2-flowered;
Fruits acorn 1-1.5 cm, ovoid; stalkless or nearly so; singly or to 3 together; cup very shallow covering 1/2 or 1/3 of nut, with nearly flat scales; maturing in 1 year;

Bark, twigs and
buds

bark brown green, smooth, becoming dark grey, warty, sulcate; twig red brown, shiny, thin (1-2 mm in diameter), soon glabrous, with rare, light lenticels; terminal bud red brown, ovoid, 1.5-3 mm, shortly ciliate;
Hardiness zone, habitat hardy zone 7; prefers dry, rocky soils;
Miscellaneous -- A. Camus : n° 384;
-- Sub-genus Quercus, section Lobatae, sub-section Acutifoliae;
-- confusion is possible with Q. albocincta, which has ovate or elliptic leaves, more veins pairs, longer teeth, longer bristle-tips and longer petioles.

-- resembles Q. affinis but this species has coriaceous leaves, petiols shorter, 2-4 (-5) pairs of teeth, and the acorn matures in 2 years;
Subspecies and
varieties
--- Q.canbyi has been described as a variety of Q.graciliformis in the south of its range (North Mexico), and differs from the type in having acorns maturing in 1 year, less lobes (4 pairs instead of 5...), and a shallower cup. In fact, it seems that it is nothing but a geographical form...For today's Mexican Authors (Silvia Romero Rangel, 2006), the accepted name is Q.canbyi, and Q.graciliformis is the synonym...
--- Q.alamarensis : for today's Mexican Authors (Susana Valencia-Avalos, 2004), this taxon described by Muller is doubfull, maybe a hybrid or a morphological, isolated variation...
--- Q.langtry (Langtry Oak) ; first considered as synonymous for Q.gravesii in 1850, is currently defined as a member of the graciliformis-canbyi group; discovered near Langtry (Texas), it bears 2 years maturing acorns and a greater number of lobes (5-7 instead of 2-5); but more studies are necessary to precise the taxonomical place of this species; hardiness zone : 7;
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