Annual Ragweed

Ambrosia artemisiifolia Annual Ragweed

DESCRIPTION

Annual herb to 2m high with rounded stems and basal rosette of leaves during early growth. Green to grey-green fern- like leaves 1–16cm long by 1–5cm wide are finely hairy to near glabrous.

FLOWERS AND FRUIT

Separate male and female flowerheads on same plant from summer to early winter; drooping yellow-green male flowerheads in elongated spike-like clusters to 20cm long at branch tips; tiny female flowerheads from upper leaf forks. Small brown or blackish top-shaped achenes 2-5mm long contain a single seed; fruit is woody when mature and has a pointed ‘beak’ 1-2mm long.

HABITAT AND RANGE

Disturbed areas, roadsides, wasteland and cultivation in scattered locations from Sydney to the wet tropics. Native to North America, this is a Category 3 weed, which must not be distributed or disposed of.