Erect, rhizomatous herb or subshrub to c. 80 cm high; stems narrowly 4-winged. Leaves broadly ovate to obovate, 10–35 mm long, 5–20 mm wide, usually cordate at base, margins minutely black-dotted, 3–7-nerved from near base. Flowers in rather dense corymbose cymes; sepals lanceolate to triangular, acute to acuminate, 3–5 mm long, sparsely black-dotted toward the apex (occasionally some lacking black dots); petals up to twice as long as sepals, yellow, sparsely black-dotted toward the tip; stamens numerous, slightly shorter than petals, shortly fused into 3 bundles; styles 3. Capsule ovoid, c. twice as long as sepals; seeds cylindric, c. 0.8 mm long, finely reticulate. Flowers Jan.–Mar.
*GipP, *HSF. Alos naturalised Tas. Of restricted occurrence, in damp areas (creek and swamp margins) mostly around the Dandenong Ranges and nearby areas (e.g. Woori Yallock Ck near Yellingbo, Olinda Ck, Jumping Creek near Wonga Park, Toomuc Ck near Pakenham), also Frankston, Phillip Is. Also fringing ornamental lakes at the Royal Botanic Gardens, South Yarra.
A declared weed in several areas.
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