Oaks of the World

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  Quercus x robusta
Author C.H.Muller 1934 Torreya 34: 119
Synonyms emoryi x gravesii
Local names Chisos mountains oak
Range Texas (Chisos Mountains, in wet canyons), to 1500 m;
Growth habit reaches 13 m; spreading branches;
Leaves 6-12 cm long, 2-5 cm wide; deciduous; coriaceous, stiff; broadly lanceolate or oval; apex pointed, often long acuminate; base subcordate, or slightly cuneate or truncate, or subcordate; margin unevenly lobed, with 3-5 pairs of aristate teeth, rounded and deep sinuses; both sides glabrous, with persistent hairs above along midrib; beneath frequent axil tufts; 8 vein pairs remotely raised above, prominent beneath; petiole 1-2cm long, pubescent;
Flowers female carkin 5-6 mm or even shorter, bearing1-2 fruits;
Fruits acorn 1.5-2 cm long, oblong, subcylindrical, sometimes elongated, puberulent, with longitudinal stripes; enclosed for 1/4 or 1/3 of length in cup with pointed, tomentose, appressed scales; maturing in 2 years;

Bark, twigs and

bark dark and furrowed, rough; twigs dark brown, 2-3 mm thick, tomentose at first, soon glabrous; numerous small lenticels; bud oblong 3-4 mm;
Hardiness zone, habitat prefers wet places, in mountains;
Miscellaneous -- A. Camus : tome 3, p. 424, n° 428;
-- For C.H. Muller, and for Govaerts & Frodin (1998), it's a true species (fixed hybrid);

Subspecies and