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Hemlock (Conium maculatum)

Hemlock is a serious poisoning risk because all parts of the plant are poisonous to people and livestock and can cause death by respiratory paralysis if eaten. It can also establish rapidly, replace other plants and reduce the grazing value of land.

Key facts

Type: Weed, herb.

Native to: Europe, west Asia and north Africa.

Established in: QLD, NSW, ACT, VIC, TAS, SA, WA.

Other names: Poison Hemlock, Poison Parsley, Spotted Hemlock, Wild Carrot Fern.

Best time to act: Look for seedlings mainly after autumn germination, sometimes in spring, and treat before flowering, which may occur in the first or second spring after germination.

Identification

  • A robust, hairless herb that can grow to 2.5 m tall, with a long white taproot.
  • Its hollow, waxy-looking green stems have purple to reddish-brown blotches.
  • Large, alternate leaves are deeply divided and fern-like; crushed leaves have an acrid smell.
  • Numerous small white, cream or rarely light-pink flowers form umbrella-shaped heads at the ends of stems.
  • The small oval fruit is 2.5–4 mm long, with 10 well-developed ribs.
  • Look-alike: Wild Carrot (Daucus carota) has hairy stems without purple blotches, crushed leaves that smell carroty, and fruit with short spines rather than smooth ridges.
  • Look-alike: Fennel (Foeniculum vulgare) has narrower leaf segments, foliage that smells of aniseed when crushed, and yellow flowers.

Where it grows

In Australia it occurs in moist, often shady disturbed places such as riverbanks, creeks, roadsides, pasture edges and stockyards, and is recorded across all states and territories.

Why it matters

  • All parts are poisonous when eaten and can cause serious illness or death in humans and livestock through respiratory paralysis.
  • Cattle and pigs appear more susceptible than sheep and goats, and young animals more susceptible than old; the plant can taint milk and affect yield.
  • Hemlock can replace native species in disturbed or riparian sites and replace desired plants in urban riparian areas.
  • Once established, it can preclude the growth of other plants and reduce the grazing value of land.

How it spreads

  • Hemlock spreads only by seed; water carries seed naturally, and wind may spread it short distances.
  • People can spread seed over longer distances on farm or horticultural machinery, vehicles, contaminated soil and clothing.
  • Seed may also be moved as a contaminant in farm produce such as hay or silage.

Control options

  • Use a long-term management plan and combine methods to remove infestations and prevent seed set.
  • Use registered herbicides before flowering; spot spraying is more effective than boom or mist spraying, and keep animals away from treated areas.
  • Hand-pull or hoe individual plants, or cultivate larger areas before flowering; wear gloves when hand-pulling and follow up to deal with seedlings.
  • Mowing or slashing before flowering can help, but plants may regrow from their bases; sow vigorous pasture to inhibit seedlings and avoid grazing because the plant is highly toxic.

Hygiene and washdown

  • Avoid moving contaminated soil, seed on clothing, or contaminated hay and silage; farm and horticultural machinery and vehicles can also spread seed.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Regionally controlled / restricted weed (varies by region). Where it is regionally controlled, landowners must take all reasonable steps to prevent its growth and spread on their land. Where it is a restricted weed, trade in it (including the plant, its seed or contaminated material) is prohibited.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources