Jacobaea vulgaris Gaertn.

• an upright and long-lived herbaceous plant that forms a basal rosette of leaves during the early stages of growth.
• it later produces one or more upright stems that are much-branched towards the top of the plant.
• its deeply-divided leaves are dark green and mostly hairless above, and somewhat paler and hairy underneath.
• its bright yellow flower-heads (20-25 mm across) are borne in dense clusters at the tops of the branches and have 12-15 elongated 'petals'.
• the bases of the flower-heads are surrounded by about thirteen small greenish bracts that have black or brown tips.
• it gives off an unpleasant smell when damaged.

[From: Environmental Weeds of Australia]