Summergreen herb; stems erect, ± minutely glandular-hairy, to c. 1 m tall, arising from underground rhizomes. Lvs opposite, shortly petiolate to subsessile. Lamina 4-11 × 1.5-4 cm, lanceolate to ovate or elliptic, glabrous above, minutely glandular-hairy beneath and dotted with black glands, entire; base cuneate to rounded; apex acute. Panicle terminal, many-flowered, glandular-puberulent, with leaflike bracts subtending lower branches; upper bracts subulate to lanceolate. Pedicels often > fls. Calyx 4-5 mm long; lobes lanceolate, acuminate, rounded at base, glandular-ciliate and dark-margined. Corolla limb c. 2 cm diam., yellow, often with pinkish flush towards base, dotted with minute glands; lobes 7-10 mm long, ± elliptic-oblong. Stamens 3-5 mm long; filaments united to c. ⅓ length, densely glandular-scaly. Style > stamens, glabrous. Capsule 3-4.5 mm diam., ± globose. Seed broad-ellipsoid, flattened with thick rounded margin.