Asteraceae

Parthenium hysterophorus

Common Names: Parthenium weed

Plant Form: Annual rosette multi-branched herb. Size: 50 cm to 2 m tall. Stem: Erect and ribbed single stem, many branched above. Leaves: Initially rosette, upper leaves deeply divided, covered in soft fine hair. Flowers: Creamy white, in circular clusters, loosely branched in flowerhead. Dotted with resin. Fruit and Seeds: Seeds tiny 1-2 mm across, triangular, brown to black. Habitat: Roadsides, paddocks, flooded areas. Distinguishing Features: Creamy white daisy-like flower clusters, and ribbed stems distinguish from Ragweed (Ambrosia species). Impacts: Highly toxic to animals and humans, threatens biodiversity.