Emex australis Steinh.

Three-cornered Jack

Ann. Sci. Nat. Bot. 7 fig., ser. 2 t. , 16 (1838) APNI

Taxonomic status:Accepted

Occurrence status:Present

Establishment means:Naturalised

Prostrate or decumbent, somewhat fleshy herb with stems spreading for c. 50 cm from a basal rosette. Leaves ovate to broadly oblong, 2–8 cm long, 1–5 cm wide, obtuse at apex, truncate or shallowly cordate at base; margins often undulate and/or crenate; petiole normally longer than lamina. Male inflorescences c. 2–7 cm long; perianth segments c. 2 mm long. Female flowers subsessile, fruiting perianth 7–11 mm long, 4–6 mm wide at the widest point (just below the spines), the sides broadly ribbed and indented, with a basal concavity, spines slender, spreading to c. 10 mm diam., inner segments c. 3 mm wide at apex of tube, rounded, with a short apical mucro, reticulate. Nut ovate, broadly trigonous below, triquetrous toward the acute apex, 4–5 mm long, brown, smooth, retained within the woody fruiting perianth. Flowers most of year, mainly Apr.–Nov.

*GipP, *LoM, *MuF, *MuM, *MSB, *OtP, *RobP, *VRiv, *VVP. Naturalized all mainland States. Native to southern Africa. Moderately common in north-western Victoria on road verges and irrigated cropland, occasional in heavier loamy soils in the vicinity of lakes and watercourses (e.g. Lake Hattah, Murray River floodplain). Sporadic elsewhere, e.g. near Melbourne and Geelong, possibly spreading by contaminated seed or hay.

A serious agricultural weed in Western Australia and South Australia. There are some reports of this species hybridizing with the less common E. spinosa (Parsons & Cuthbertson 1992).

Source: Walsh, N.G. (1996). Polygonaceae. In: Walsh, N.G.; Entwisle, T.J. (eds), Flora of Victoria Vol. 3, Dicotyledons Winteraceae to Myrtaceae. Inkata Press, Melbourne.
Hero image
Distribution map
life Life
kingdom Plantae
phylum Tracheophyta
superorder Caryophyllanae
family Polygonaceae
genus Emex
Higher taxa


Source: AVH (2014). Australia's Virtual Herbarium, Council of Heads of Australasian Herbaria, <http://avh.chah.org.au>. Find Emex australis in AVH ; Victorian Biodiversity Atlas, © The State of Victoria, Department of Environment and Primary Industries (published Dec. 2014) Find Emex australis in Victorian Biodiversity Atlas
  Bioregion Occurrence status Establishment means
Lowan Mallee present naturalised
Murray Mallee present naturalised
Victorian Volcanic Plain present naturalised
Victorian Riverina present naturalised
Murray Scroll Belt present naturalised
Robinvale Plains present naturalised
Murray Fans present naturalised
Gippsland Plain present naturalised
Otway Plain present naturalised

State distribution

Distribution map
Western Australia
Northern Territory
South Australia
New South Wales
Australian Capital Territory