Quercus delgadoana Valencia & al.

Mexico, in the Sierra Madre Oriental (Hidalgo, Puebla, Veracruz); 1400-2200 m;

25 m tall; trunc to 1 m in diameter;

7-18 x 1.5-5 cm, narrowly oblong, elliptic or lanceolate; leathery; both sides glaucous, but paler beneath; apex pointed or acuminate, aristate; base rounded ou cuneate; margin entire, slightly thickened, revolute; adaxially hairless, dull, grey-green somewhat glaucous, without stellate or glandular trichomes; abaxially glabrous or with sometimes some fasciate hairs at axils; (9-)14-20 vein pairs, slightly impressed or nearly flat above and slightly raised beneath, parallel, nearly straight, branched and anastomosed near margin; slightly papillar epidermis; petiole thin, 2-6 mm long, darkened near base;

pistillate inflorescence at leaves axils, with flowers solitary or paired on a 1.8-2 mm long peduncle;

acorn ovoid, 2 cm long, 1,2 cm wide, glabrous outside; solitary or paired, short hairless peduncle; cup conical or slightly turbinate, 0.6-1.5 cm in diameter, with margin not rolled, ovate scales that are greyish near base, more or less glabrous; maturing in 2 years, in October-November;

– Sub-genus Quercus, section Lobatae, Series Erythromexicanae; – Very rare species. Threatened (IUCN Red List Category : EN) – Differs from Q. sapotifolia which has acorns maturing first year, and leaves that are not slightly glaucous ; it differs also from Q. laurina and from Q. affinis which have a flat blade margin and fewer secondary veins (6-10 and 5-9); see HERE to compare with other whole-leaved oaks .