Ambrosia psilostachya DC.

Perennial Ragweed

Prodr. 5: 526 (1836) APNI

Taxonomic status:Accepted

Occurrence status:Extinct

Establishment means:Introduced

Erect perennial herb to 2 m high, stoloniferous, often forming dense colonies; stems simple or branched above, strigose to scabrous. Leaves alternate, subsessile, lanceolate to ovate in outline, mostly 4–12 cm long and 2–4 cm wide, pinnatipartite with lanceolate segments 2–4 mm wide, surfaces appressed-hairy. Inflorescences often numerous, 3–12 cm long. Male capitula numerous, 2–3 mm diam., cream or greenish; peduncles c. 1 mm long; florets many, not exceeding involucral bracts. Female capitula in small clusters in upper axils; fruiting capitula turbinate, 3–4 mm long, reticulate, 5-ribbed, with 5 short spines above and a longer central beak. Flowers spring and summer.

Also naturalised WA, SA, Qld, NSW. Native to North America. Known from the Corryong, Nagambie and Shepparton areas but probably more widespread. Grows along roadsides and other disturbed sites. Declared a noxious weed in Victoria.

Source: Jeanes, J.A. (1999). Asteraceae. In: Walsh, N.G.; Entwisle, T.J. (eds), Flora of Victoria Vol. 4, Cornaceae to Asteraceae. Inkata Press, Melbourne.
Updated by: Val Stajsic, 2018-03-27
Hero image
Distribution map
life Life
kingdom Plantae
phylum Tracheophyta
superorder Asteranae
order Asterales
family Asteraceae
genus Ambrosia
Higher taxa


Source: AVH (2014). Australia's Virtual Herbarium, Council of Heads of Australasian Herbaria, <>. Find Ambrosia psilostachya in AVH ; Victorian Biodiversity Atlas, © The State of Victoria, Department of Environment and Primary Industries (published Dec. 2014) Find Ambrosia psilostachya in Victorian Biodiversity Atlas
  Bioregion Occurrence status Establishment means
Murray Mallee extinct introduced
Victorian Riverina extinct introduced
Northern Inland Slopes extinct introduced

State distribution

Distribution map
Western Australia
South Australia
New South Wales