Introduced annual forb to 1.2m tall. Three-branched yellow spines at the bases of the leaves. Leaves alternating up the stems, 2-10cm long, 6-30mm wide, flat, shiny dark green above and more or less hairy, hairy below, edges entire, toothed, or three-lobed, tips pointed. Individual flower heads tiny (less than 3mm across), male and female flowers on the same plant. Male flower heads pale green or creamy green in clusters of 2-8 at the tops of the stems or at the bases of the upper leaves, female flower heads yellowish green to brown, usually single, stemless, at the bases of the leaves. Burrs hairy, with many hooked spines. Noxious weed Wentworth Shire. Declared plant in SA. Noxious weed in Vic.
Description and photo in G.M. Cunningham, WE Mulham, PL Milthorpe and J H Leigh (1981 and later printings) Plants of Western New South Wales page 727
PlantNET description with line drawings and photo of dried specimen: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Xanthium~spinosum
Weeds of Australia Biosecurity Queensland Edition description: http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/Xanthium_spinosum.htm