Family: Apiaceae, formerly Umbelliferae (carrot, parsley etc)

Status: Declared noxious in category W2 (must be continually suppressed and destroyed) in Eurobodalla LGA.

Description:
Robust annual or biennial herb 1 to 2m high with zigzagging stems, which have a whitish bloom, are finely blotched brown or purple, and are hollow. The leaves are finely divided and ferny in appearance. Flowers are small, white, and carried in branching umbrella-shaped heads. Hemlock is said to have a "mousy" smell when crushed.

Preferred habitat and impacts:
Usually found on waste ground in moist conditions, such as river banks and around the edges of pasture. Hemlock seldom forms large stands on the south coast, but it is a significant weed because all parts of the hemlock plant are poisonous to humans and livestock if eaten. It causes death by respiratory paralysis. Handling the plant may cause dermatitis in some people. It also taints milk and can affect yield, and if consumed in sub-lethal doses, may cause birth deformities. It is rarely eaten green by stock, but may be consumed when incorporated into hay or sileage.

Dispersal:
Seed is spread by water, machinery or vehicles, or in contaminated soil or by wind over short distances.

Look-alikes:
Another weed in the same family, wild carrot (Daucus carota ) is common on roadsides. It has similar heads of white or pinkish flowers, and the crushed leaves smell carroty. Fennel (Foeniculum vulgare ) has a similar habit but narrower leaf segments and yellow flowers. Control both these weeds as for hemlock.

A tall annual or biennial native herb Trachymene anisocarpa has similar branched umbrella-like heads of white flowers to those of wild carrot and hemlock. Its leaves are less divided, being composed of three lobed leaflets. It grows in wet sandy soils close to swamps.

Control:
Hand chip small infestations or spot spray actively growing young plants before they elongate into the flowering stage, preferably with a selective woody weed herbicide. Slashing just before flowering may kill the plants, or some new growth may occur and need follow-up treatment.