Quercus chihuahuensis Trel.

Mexico (Aguascalientes, Chihuahua, Durango, Guanajuato, Jalisco, Nayarit, Nuevo Leon, Sinaloa, Sonora, Zacatecas, San Luis Potosi); 1400 - 2000 m;

5-8 m; trunk to 0.3-0.4 m in diam.; spreading crown;

4-10 x 2-5 cm; late deciduous; leathery; oblong-oboval or elliptic; not convex; apex obtuse, sometimes subacute or mucronate; base rounded or subcordate; margin entire or sinuate-dentate (if so, with 1-4 pairs of teeth ending in a mucro), flat or slightly revolute, thick; yellowish blue-green, at first densely fascicled (3-8 rays) tomentose above, then glabrescent; paler below, densely whitish-yellow tomentose with stipitate fascicled hairs (stalk more than 0.08 mm long, to 0.2 mm); 8-10 vein pairs, both sides flat or sometimes slightly impressed adaxially; epidermis pale green or glaucous, papillose and glandular; petiole 3-10 mm, tomentose;

spring; staminate carkins tomentose, 2-5 cm long, with numerous flowers; pistillate flowers at the tip of a stout, tomentose, to 5 mm long peduncle.

acorn 1.5 cm, ovoid, light brown; solitary or paired; peduncle pubescent 1.5-5 cm; 1/2 enclosed by cup; cup with straight rim and densely tomentose scales; maturing first year from June to November; cotyledons connate;

– A. Camus : n° 256 ; – Sub-genus Quercus, Section Quercus; Series Leucomexicanae, Group Chihuahuenses; – Rare in USA, where it forms hybrids with Q.grisea and Q.arizonica (= Q. x undata Trel.) – For Zavala-Chavez, 2003, Q.infralutea is a variety of Q.invaginata . – Possible confusion with Q. grisea , which has whitish, stalkless, stellate trichomes; also with Q. deserticola which has midrib and secundary veins impressed above, stipitate and sessile fasciate hairs below (the stalk less than 0.07 mm long) and margins markedly revolute. – Resembles also Q. praeco, which differs in having the rim of the cupule rolled inside, the underside covered with subsessile fascicled hairs, stipitate ones (stalk nearly 0,1 mm long) and stellate other ones.