Blue billy goat weed. Ageratum houstonianum
Native to tropical America
Forms dense patches on disturbed sites on roadsides, hind-dunes and headlands. A problem on the north coast of NSW.
Form: Erect herb, 0.3 - 1m high.
Flower: Small, light blue to mauve. Flowers throughout the year mainly summer to autumn.
Fruit/Seed: Small dry seed sparsely hairy at one end.
Control: Hand-pull or cut off at the base before it flowers.