Ageratina adenophora (Spreng.) R.M.King & H.Rob.

• a long-lived herbaceous plant or small shrub growing up to 2 m tall.
• it produces upright, branched stems from a woody rootstock.
• its stems are covered in sticky hairs when young and bear pairs of oppositely arranged leaves.
• its leaves are relatively broad, diamond-shaped or almost triangular in shape (4-15 cm long and 3-9 cm wide), and have toothed margins.
• its small white flower-heads are borne in dense clusters at the tips of the branches.
• its roots are yellowish in colour and give off a distinct carrot-like smell when broken or damaged.

[From: Environmental Weeds of Australia]