Myriophyllum caput-medusae Orchard

Coarse Water-milfoil

Brunonia 4: 53 (1981) APNI

Taxonomic status:Accepted

Occurrence status:Present

Establishment means:Native

Perennial aquatic herb; stems 0.3–2 m long, mostly 3–4 mm diam., rooting mainly at the base, emergent parts much branched. Leaves dimorphic, in whorls of 3–5; submerged leaves ovate, mostly 12–20 mm long, pectinate, with 16–20 pinnae; emergent leaves oblong to ovate, mostly 6.5–8 mm long, alternate towards apex, glaucous, sometimes purplish, margins entire. Bracteoles linear, 0.7–0.9 mm long, cream to pale green; flowers solitary, sessile. Male flowers: sepals 4, triangular, c. 0.15 mm long; petals 4, 2.1–2.6 mm long, yellow to reddish, caducous; stamens 8. Female flowers: sepals absent; petals vestigial; ovary 4-celled, styles clavate, stigmas red. Fruit shortly cylindric, olive-brown; mericarps cylindric, 1.4–1.5 mm long, rounded, densely spinulose, with an apical collar. Flowers Oct.–Mar.

CVU, EGL, EGU, GipP, Gold, HNF, HSF, MonT, MuF, MuM, NIS, OtP, OtR, RobP, VRiv, VVP, WPro, Wim. Also SA, NSW. Scattered widely throughout much of Victoria particularly along the Murray River and its tributaries. Grows in lakes, billabongs and slow-flowing watercourses.

A distinctive species closely allied to Myriophyllum porcatum, from which it is distinguished mainly by its fruit ornamentation, emergent leaf shape and arrangement, and its perennial lif cycle (Orchard 1985). The distinctive spines on the mericarps are not apparent except in fully mature fruit.

Reported to be an occasional weed in smaller irrigation channels in Victoria and, less commonly, in New South Wales.

Source: Jeanes, J.A. (1996). Haloragaceae. In: Walsh, N.G.; Entwisle, T.J. (eds), Flora of Victoria Vol. 3, Dicotyledons Winteraceae to Myrtaceae. Inkata Press, Melbourne.
Updated by: Val Stajsic, 2017-08-16

Orchard, A.E. (1985). Myriophyllum (Haloragaceae) in Australasia. II. The Australian Species, Brunonia 8: 173-291.

Hero image
Distribution map
life Life
kingdom Plantae
phylum Tracheophyta
superorder [Saxifraganae]
order Saxifragales
family Haloragaceae
genus Myriophyllum
Higher taxa


Source: AVH (2014). Australia's Virtual Herbarium, Council of Heads of Australasian Herbaria, <>. Find Myriophyllum caput-medusae in AVH ; Victorian Biodiversity Atlas, © The State of Victoria, Department of Environment and Primary Industries (published Dec. 2014) Find Myriophyllum caput-medusae in Victorian Biodiversity Atlas
  Bioregion Occurrence status Establishment means
Murray Mallee present native
Wimmera present native
Victorian Volcanic Plain present native
Victorian Riverina present native
Robinvale Plains present native
Murray Fans present native
Gippsland Plain present native
Otway Plain present native
Goldfields present native
Central Victorian Uplands present native
Northern Inland Slopes present native
East Gippsland Lowlands present native
East Gippsland Uplands present native
Wilsons Promontory present native
Highlands-Southern Fall present native
Highlands-Northern Fall present native
Otway Ranges present native
Monaro Tablelands present native

State distribution

Distribution map
Western Australia
South Australia
New South Wales