Family: Lamiaceae (mints)

Description:
A low bushy aromatic perennial herb to about 30 cm high, with hairy, wrinkled, grey-green round to oval, toothed leaves in opposite pairs. Flowers are small and white, carried in dense clusters surrounding the stems in the leaf axils. Fruits are a burr, which readily attaches to wool, clothing, etc.

Preferred habitat and impact:
Colonises over-grazed pasture and other areas of bare soil, such as stock camps and rabbit warrens. More common in drier inland areas.

Burrs contaminate fleeces, and the meat from stock forced to graze on it is tainted. However, it is not palatable and generally avoided, which enables it to become dominant in over-grazed paddocks. Young seedlings are not competitive in vigorous pasture, but it is likely to become established after droughts, particularly if feed has been imported from contaminated areas.

Dispersal:
Seed is spread in hay, on animals or clothing, and will be still viable after passing through horses. Can also spread in water.

Look-alikes
Native perennial herbs in the genus Plectranthus have similar furry rounded toothed leaves, but their growth habit is more open and sprawling, and flowers are blue, in long terminal spikes. Like horehound, they are in the mint family, and have slightly aromatic foliage. They tend to grow in rocky situations, very rarely in pasture unless rock outcrops are present.

Control:
Do not over-graze, and control rabbits. Seedlings are not very competitive, and need bare ground to establish. Chip plants out. Burning can be used to stimulate seed germination, followed by summer cultivation, for large infestations. This may need to be repeated. Spot spraying with selective or non-selective herbicides. A surfactant will improve the take-up of herbicides.