Thought to be native to North and Central America and introduced to Australia as an impurity in cotton seed, this weed is commonly found on disturbed ground, along rivers and creeks, on roadsides and in old cultivated areas.
- Annual branched herb to 2 m high.
- Stems are rough to touch and often tinged purple.
- Leaves are dark-green, purple veined, with 3-5 large lobes resembling a grape leaf, margins coarsely toothed, lower leaves opposite, upper leaves alternate.
- Greenish flowers in clusters, male flowers inconspicuous at the end of branches and soon fall off, female flowers in leaf axils develop burrs.
- Brown hairy burrs 2-3 cm long, with many hooked spines and two stout straight spines at the end, contain two seeds in separate compartments.