Erect shrub, 1-3 m tall. Stem much branched, opposite decussate, glabrous or slightly pubescent, more or less herbaceous, bark of woody portion ash-coloured and usually with purple streaks. Leaves opposite, 7-20 x 4-10 cm, elliptic, oblong or ovate, acute to acuminate, attenuate, glabrous or pubescent, specially on nerves beneath, lateral nerves 10-20 pairs, arcuate; petiole 1-2 cm long; stipules broad triangular, cuspidate, ensiform or abruptly acuminate. Inflorescence trichotomously branched with panicles of head-like clusters. Flowers bluish-purple or white, fragrant, c. 1.5 cm long; bracts c. 2 mm long, leafy; bracteoles many, surrounding each fascicle of flowers, subulate, vinous. Calyx teeth 5, linear-subulate, hispid, persistent; tube narrow. Corolla-tube slender, widened somewhat towards the mouth, pubescent; lobes 5, spreading, oblong or ovate, acute, valvate in bud, c. 2 mm long. stamens included, filaments very short, anthers erect. Style filiform, as long as corolla-tube; stigma 5-cleft. Capsule 2.5-4 mm long, ovoid, 5-valved at the top, pubescent, black, compressed. Seeds 5 or less by abortion, surrounded by loose reticulate aril.