Stems 1 or 2 from one root, 50-120 m tall, simple, glabrous or very sparsely hispidulous. Cauline leaves 3-or 4-verticillate or-subverticillate, shortly petiolate; blade ovate, elliptic, or elliptic-linear, 5-13 × 0.4-4.5 cm, both surfaces glabrous or sparsely hispidulous along veins, margin regularly or irregularly dentate or serrate. Inflorescence a panicle of cymes, branches sometimes almost verticillate; pedicels usually less than 1 cm. Hypanthium ellipsoid or obovoid-obconic, glabrous; calyx lobes filiform-subulate, 5-10 × less than 1 mm, margin with 1 or 2 pairs of denticles. Corolla blue or purple-blue, funnelform, 1.8-2.5 cm; lobes ovate-deltoid, 5-6 mm. Disk shortly tubular, 0.8-1.5 mm, glabrous. Style slightly shorter than corolla. Capsule oblong, ca. 10 × 4-5 mm. Seeds orange-yellow, ellipsoid, ca. 1.5 mm. Fl. Aug-Sep, fr. Sep-Oct. 2n = 34*.
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