Stachytarpheta jamaicensis (L.) Vahl
Vahl, M. (1804) Enumeratio Plantarum 1 : 206.
Snakeweed, Light Blue; Snakeweed, Jamaican; Snakeweed, Jamaica; Snakeweed; Pale Blue Snakeweed; Jamaican Snakeweed; Light Blue Snakeweed; Snakeweed, Pale Blue; Jamaica Snakeweed; Bastard Vervain
Usually flowers and fruits as a shrub about 1-2 m tall but also flowers when smaller.
Inflorescence axis about 3-5 mm diam., furrows from the immersed flowers narrower than the axis. Calyx tubular, about 5-7 mm long, lobes about 1 mm long. Corolla tube about 7-11 mm long, lobes about 2-3 x 2-3 m. Inner surface of the corolla tube clothed in long, erect, gland-tipped hairs. Stamens two, staminodes two. Anther locules borne one above the other with their long axes in line. Pollen grains often appear to be sterile.
Cotyledons ovate, about 6 x 4 mm, petiole quite long. First pair of true leaves opposite, margin toothed, sparsely hairy on the lower surface. At the tenth leaf stage: leaves ovate, elliptic or obovate, margin toothed, leaf blade sparsely punctate on the underside, gradually tapering into the petiole. Seed germination time 152 to 533 days.
An introduced species originally from tropical and subtropical America and the West Indies, now a pantropic weed. naturalised in WA, NT, CYP, NEQ, CEQ and southwards as far as south-eastern Queensland. Altitudinal range in northern Australia from near sea level to 700 m. Grows in disturbed areas in rain forest particularly along roads but is more common as a weed on agricultural land.