Quercus helferiana A. de Candolle, Prodr. 16(2): 101. 1864; Q. prainiana H. Léveillé.

Trees to 20 m tall. Branchlets densely pale brown tomentose, glabrescent by 3rd year. Petiole 1-2(-3) cm, pale brown tomentose; leaf blade oblong-elliptic, ovate, or elliptic-lanceolate, 12-15(-22) × 4-8(-9.5) cm, densely pale brown tomentose when young, abaxially pale grayish brown tomentose with age, adaxially glabrescent except for basal part of midvein, base broadly cuneate to rounded, margin crenate, apex acuminate to obtuse; midvein adaxially impressed; secondary veins 9-14 on each side of midvein. Infructescences 1-2 cm; rachis ca. 2 mm thick, pubescent. Cupule discoid, 5-10 mm × 1.8-2.5 cm, enclosing 1/3-1/2 of nut, outside pale brown tomentose, wall 1.2-2 mm thick; bracts in 8-10 rings, margin denticulate to subentire. Nut oblate, 1-1.6 × 1.5-2.2 cm, gray villous, apex depressed; scar 1.2-1.4 cm in diam., flat to concave at maturity. Fl. Mar-Apr, fr. Oct-Nov.

900-2000 m. Guangdong, Guangxi, S Guizhou, S to SW Yunnan [NE India, Laos, Myanmar, N Thailand, Vietnam]