Common and scientific names
Hemlock, carrot fern
Conium maclatum L.
Origin and distribution
Hemlock is a biennial or occasionally an annual plant which originated in Europe, western Asia and North Africa and was deliberately introduced to Australia. It prefers moist, neglected situations and can be found in most areas of Victoria. It is usually unimportant as an agricultural weed but sometimes invades pastures and areas of cultivation. As an environmental weed it has invaded lowland grassland and grassy woodland, riparian vegetation and warm temperate rainforest.
Hemlock reproduces from seeds which usually germinate in autumn. Annual plants flower in the first spring, produce seeds and die in summer. Biennial plants remain in a vegetative state until their second spring, flower, then set seed and die in their secondsummer.
Stems - Erect, up to 3 m high but often less than 2 metres; strong, hairless, hollow except at nodes, longitudinally grooved; pale green, blotched with purple and emitting an offensive odour when damaged.
Leaves - Fern- or carrot-like, 12 to 25 cm long but up to 50 cm, hairless, alternate, emitting a strong, acrid ('mousey') odour when crushed. Leaf stalks are deeply cupped at the base and surround the stem.
Flowers - White or greenish-white, 2 to 4 mm diameter with five petals; numerous, in dense umbrella-like clusters at the ends of the stems. Present in spring to early summer.
Seeds - Dark-grey to brown, 3 mm long, globular with five prominent wavy ridges.
Roots - Long white taproot which may be branched.
Hemlock contains five toxic alkaloids which vary in concentration due to climatic conditions. The fruit, vegetative parts and roots are all poisonous to humans and stock. The Greek philospher Socrates is said to have been killed with hemlock. In Victoria a child died from hemlock poisoning in 1994. Handling the plant can cause dermatitis in some people.
Cattle, pigs, horses and poultry are more susceptible to hemlock poisoning than sheep and goats. The plant is rarely grazed when green and is more likely to be consumed in hay, chaff or silage. Symptoms of hemlock poisoning in stock include dullness, loss of muscular power, stumbling and falling, nausea, dilation of pupils and complete paralysis. Symptoms may show as quickly as 12 minutes after the plant is eaten and death may occur in 2 to 3 hours.
Hemlock grows rapidly after autumn rains, and on disturbed soils can exclude most other vegetation. It does not readily invade well managed established pastures.
Seeds can be spread by animals, machinery, water, agricultural produce including hay and silage, gravel, soil extraction and to a limited extent by wind.
Prescribed measures for the control of noxious weeds
- Application of a registered herbicide
- Physical removal
Important information about prescribed measures for the control of noxious weeds.
Other management techniques
Changes in land use practices and spread prevention may also support hemlock management after implementing the prescribed measures above.
- Contact your local landcare or friends group for further assistance and advice.
- Call the Customer Service Centre on 136 186.
- Weeds Australia
McBarron, E.J. (1983) Poisonous Plants Handbook for Farmers and Graziers. Melbourne, Inkata Press.
Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious Weeds of Australia. Melbourne, Inkata Press
This Information Note was developed by Department of Primary Industries
Prepared by Ross Williamson, 1997. Updated by Ian Faithfull, April 1998. Updated by Melanie Martin, DPI, October 2006. Chemical information supplied by Chemical Standards Branch August 2006. Updated by Adam Kay, DPI, August 2007.