Roots carrot-shaped. Main stems scrambling or twining, fertile, sparsely villous; branches sterile or fertile, with subopposite leaves. Leaves on main stems alternate, those on branches subopposite; petiole 5-18 mm, hirsute; blade ovate or deltoid, 7-23 × 5-17 mm, abaxially hispid, adaxially hispidulous, base rounded or truncate, rarely shallowly cordate, margin mostly entire or sinuous, or very obscurely crenate, apex acute or obtuse. Flowers solitary, terminal on main stems and some branches, slightly pendent; pedicels 1-2.5 cm, sparsely hispid. Calyx tube adnate to ovary up to middle, hemispherical, glabrous or rarely sparsely hairy; lobes ovate to lanceolate, 5-9 × 3-5 mm, subentire, sparsely hispid, apex acute; sinus between calyx lobes narrow and acute at anthesis. Corolla greenish yellow or pale blue, tubular, 1.5-2 cm, subglabrous, shallowly lobed. Stamens glabrous; filaments slightly dilated at base, ca. 3 mm; anthers ca. 3 mm. Capsule 10-15 × 6-12 mm. Seeds brown, ellipsoid, ca. 1.5 mm. Fl. Aug-Sep, fr. Oct.