Perennials to 1 m tall. Rhizomes blackish, short, with few slightly fleshy rootlets. Stems erect, simple. Basal and lower stem leaves alternate; petiole flattened, 6-21 cm; leaf blade spatulate-oblong to oblong, 11-15 × 4-8 cm, base narrowed, apex obtuse, veins 5-7. Upper stem leaves opposite, sessile or short petiolate; leaf blade oblong, (3-)6-8 × 0.8-3.5 cm, both ends obtuse, veins 1-3. Inflorescences many-flowered thyrses 15-25 cm. Flowers 5merous. Pedicel 1.5-2.5 cm. Calyx lobes lanceolate to oblong, 4-8 × 1.5-2 mm, apex acute, midvein distinct. Corolla pale yellow, sometimes with blue spots, 1-1.5 cm in diam., tube 1.5-2 mm; lobes oblong, 8-11 × 3-5 mm, apex acute to obtuse. Nectaries 2 per corolla lobe, cupular, with pilose fimbriae 1.5-2 mm. Filaments 7-9 mm, base fimbriate-barbate; anthers ellipsoid, 2-2.5 mm. Style indistinct; stigma lobes suborbicular. Capsules ellipsoid, 1-1.3 cm. Seeds brown, compressed, suborbicular, 2.5-3 mm in diam., discoid winged. Fl. and fr. Jul-Aug.
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