Quercus sideroxyla Bonpl.

Mexico (Chihuahua, Coahuila, Durango, San Luis Potosi, Tamaulipas, Zacatecas); 2200-3000 m;

5-10 m tall, reaches 20 m; trunk to 0.5-1 m in diameter;

4-9 x 1.2-3.7 cm; thick, coriaceous, rough; oblanceolate to oblong or oboval; apex obtuse, sometimes acute, aristate; base subcordate to rounded; margin slightly revolute, flat, cartilaginous, dentate-serrate apically with 2-5 pairs of teeth shortly bristle-tipped; glaucous above, dull, glabrous except at base of midrib where remain some stellate, stalkless, dark trichomes; dense, yellowish-white felted tomentum beneath, made of long, sessile, multiradiate (20-30 rays) trichomes and golden glandular hairs; 5-9 vein pairs slightly impressed above, prominent beneath; abaxially reticulate, whitish, dull, papillose epidermis; petiole blackish tomentose, 5-8 mm long;

from June to August; staminate catkins tomentose, 3-4 cm long, with more than 20 flowers; pistillate inflorescences 0.5-1 cm, with 1-2 flowers;

acorn 1-1.2 cm long, ovoid sessile or sometimes with a stalk to 5 mm long; singly or paired; cup half-round 8-10 mm in diameter, enclosing 1/3 ou 1/2 of nut ; maturing in 1 year between August and September;

– A. Camus : n° 368; – Sub-genus Quercus, section Lobatae, Series Erythromexicanae; – Resembles Q. crassifolia , but differs in having the abaxial tomentum less dense, and made of stalkless trichomes (pediculate for crassifolia ), and the tomentum of twigs less dense as well; – Possible confusion with Q. microphylla , but this species has smaller, stiffer leaves, with a revolute margin .