Stem 40--100 m, usually glabrous. Leaves obovate to ovate-elliptic, 1--1.5 cm × 4--8 mm, adaxally glabrous, abaxially sparsely to rather densely pubescent, base deeply cordate, amplexicaul, apex acuminate to cuspidate. Cymes terminal and sometimes also axillary in distal part of stem, several to many flowered; rachis and pedicels papillose; pedicel 1.5--3 cm. Tepals obliquely outward spreading, pale yellow, with purple-red spots, obanceolate to narrowly elliptic, 1.6--2 cm × 4--5 mm; outer ones basally saccate. Stamens 1.5--2 cm. Ovary glabrous. Capsule 3--3.5 cm. Fl. and fr. Jun--Sep. 2 n = 26.