Citation: Royle, Ill. Bot. Himal. Mount. 1:376 (1839).

Synonymy: Serpicula verticillata L.f., Suppl. 416 (1782).

Common name: Waterthyme, hydrilla.

Description:
Submerged, much-branched, usually dioecious; leaves strongly sérrulate, linear to lanceolate, 6-40 mm long, 1-nerved.

Male flower with perianth-segments 1.2-3 mm long, the sepals broadly ovate-elliptic, the petals narrow-linear; female flowers on pedicels to 10 cm long and with a similar perianth to the male.

Published illustration: Sainty & Jacobs (1981) Waterplants of New South Wales, pp. 238, 240.

Distribution:  Grows in still or slow-flowing water to at least 3.5 m deep. S.Aust.: MU.   all mainland States.   Europe, Asia and Africa. Conservation status: native Flowering time: April and May.

SA Distribution Map based on current data relating to specimens held in the State Herbarium of South Australia

Biology: Wind-pollinated; the male flower becomes detached and free-floating, the female flower opens on the surface but remains attached.

Author: Not yet available