Burr ragweed is not palatable to stock and by forming dense stands which exclude all other plants can reduce carrying capacity. The burrs cause vegetable fault in wool and are not easily removed because of the hooked hairs. It produces large amounts of allergenic pollen which can cause hay fever.
Burr ragweed was introduced from the southern USA and Mexico. Burr ragweed infests areas of south-east Queensland and the western slopes and plains of NSW.
Burr ragweed is a perennial herb growing to 2 m high. Leaves are large up to 16 cm long and 10-15 cm wide, they are deeply divided.
Plants die back to the roots over winter but grow rapidly in spring and summer and flower in mid-summer. If dry spells occur in summer plants may die back and resprout in autumn.
Burrs form in clusters with short, stout, hooked spines.
Auld BA and Medd RW (1999). Weeds. An illustrated botanical guide to the weeds of Australia. Inkata Press, Melbourne.
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The requirements in the Noxious Weeds Act 1993 for a notifiable weed must be complied with