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Conium maculatum
Also called Hemlock, Deadly Hemlock, Carrot Fern, Fool's Parsley, Spotted Hemlock, Spotted Parsley, Poison Parsley
Poison hemlock is a fast-growing, highly poisonous biennial weed in the carrot family, with spotted hollow stems and lacy leaves. It is grown only by accident or for study; it thrives in moist, nitrogen-rich ground and spreads readily by seed.
Conium maculatum, commonly known as hemlock (British English) or poison hemlock (in North America), is a highly poisonous flowering plant and a nitrophile weed species in the carrot family Apiaceae.
The plant is herbaceous, with no woody parts, and has a biennial lifecycle. Under the right conditions, the plant grows quite rapidly during the growing season and can reach heights of 2.4 metres (8 feet) with a long penetrating root. The plant has a distinctive odour that is usually considered unpleasant and carries with the wind. The hollow stems are usually spotted dark maroon and turn dry and brown after the plant completes its biennial lifecycle.
All parts of the plant can be poisonous, but the total amount of poisonous alkaloids varies significantly with the age of the plant and between parts. The roots of young, first-year plants contain only traces of poison or none at all. The leaves of seedlings have lower levels of poison than slightly older plants. In the spring of the second year the leaves are highly toxic, though not as poisonous as the flowers or seeds later in the season. The hollow stems remain deadly for up to three years after the plant has died. However, drying causes the plant to lose a large part of its toxic compounds. Plants which grew in sunny conditions can be twice as poisonous as plants that grew in wet and cloudy conditions.
The main toxic alkaloids are coniine and γ-coniceine, also called gamma-coniceine. Intoxication is reported in diverse groups of animals including pigs, bovids, turkeys, equines, rabbits, cats, and dogs. However, songbirds are less sensitive and have reportedly become toxic from absorbing the coniine from hemlock.
The hemlock plant is native to Europe, Central Asia, and the Mediterranean region. It occurs in many British Isles counties, including in Northern Ireland. It has become naturalised in Asia, North America, Australia, and New Zealand. It is sometimes encountered around rivers in southeast Australia and Tasmania, where it has been considered an invasive species. Infestations and human contact with the plant are sometimes newsworthy events in the U.S. due to its toxicity. It spreads rapidly by seed, and is hard to eradicate as the seeds can lie dormant for up to 6 years.
Text excerpted from the Wikipedia article Conium maculatum by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.
The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.
Life form, climate and native range: World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 3.0), reformatted; see Plants of the World Online.
Pet safety from the ASPCA toxic and non-toxic plant lists.
