Quercus rugosa Née

Mexico (Aguascalientes, Baja California, Chihuahua, Coahuila, Durango, Guanajuato, Hidalgo, Jalisco, Mexico, Michoacan, Oaxaca, Sinaloa, Puebla, San Luis Potosi, Sonora, Tamaulipas, Tlaxcala, Veracruz, Zacatecas); S Arizona; Guatemala; 1200 - 3200 m; introduced in Europe in 1839 (G.B.);

5-10 m tall usually, but may reach 30 m, with trunk to 1 m in diameter; crown rounded;

4-16 x 3-10 cm; evergreen or lately deciduous; thick, strongly coriaceous, rough, convex; elliptic-oboval or nearly orbicular ; apex rounded sometimes acute, mucronate; base rounded or cordate; margin thick, flat or rolled under, cartilaginous, crenate to dentate-serrate in apical 2/3, with 3-10 pairs of mucronate teeth (mucro to 2 mm long, not curved towards the abaxial face) ; dark grey green above, lustrous, glabrous or with some stellate sessile and glandular hairs near base of midvein; beneath paler (yellowish or light brown), with 6-11-rayed, stellate, short stalked trichomes, and golden glandular hairs with concretions; 7-12 vein pairs, straight or sinuous, impressed above, prominent beneath; epidermis glaucous, bloomy, strongly bullate, papillose; petiole 5-12 mm, tomentose, pinkish;

in April; male catkins 1.5-2 cm, pubescent; pistillate catkins pubescent, with 15-20 flowers;

acorn 1.5-2.5 cm long, pointed; singly or to 8 together; peduncle 1.5-7 cm long; enclosed 1/3 or 1/2 by cup; cup 1-1.5 cm in diameter, with appressed, oval, pointed, tomentose scales, warty at base; maturing in 1 year between August and November; cotyledons distinct, often reddish;

quite hardy : zone 6 (withstands -15° C); all types of soils; prefers moist soils; slow growing;

– A. Camus : n° 219; – Sub-genus Quercus, Section Quercus, Series Leucomexicanae, Group Reticulatae; – No hybrids known; – Could be confused with Q. obtusata , but this one has foliar mucros short and curved towards abaxial face, the leaves are subcoriaceous sometimes plane, with an abaxial epidermis not or slightly bullate and margin not revolute; possible confusion with other similar oaks : see all differences HERE. - For Silvia Romero Rangel (2013), Q. ariifolia Trel. differs from Q. rugosa in having more and longer stellate stipitate trichomes, the underside of the leaves greyish (yellowish or light brown in Q. rugosa ) due to numerous, greyish, tangled trichomes ; moreover the acorn is smaller (1-1.5 cm long), on a peduncle 9-13 cm long. In 2017, S.Valencia & al. think that Q. ariifo lia Trel. is a true species, different from Q. rugosa in having a whitish-lanuginous abaxial blade surface, generally lacking amber glandular trichomes and leaves nor concave abaxially. See Q. ariifolia