Poisonous plants – hemlock

Conium maculatum

Hemlock leaf structure

Hemlock leaf structure

Hemlock is not the common species it once was, especially in farming areas like Galloway. It is as toxic to livestock as it is to humans, so farmers have all but eliminated it from inland areas. It is most commonly found coastally, having a preference for sandy soils, but that’s not to say it doesn’t lurk inland too. It is more common in E Scotland and S England.

It grows up to 2m tall, and has more delicate looking (fern-like) leaves and white flower umbels than many of its carrot family relatives. Cow parsely has very similar leaf structure . The key diagnostic of poison hemlock is its hairless, cylindrical, red spotted flowering stems. It also has an unpleasant mousy smell.

For a full rundown on how to distinguish poison hemlock from cow parsley, please see my post on cow parlsley.

Hemlock stem

Hemlock stem

Coniine is the main active toxin which attacks the central nervous system, leading to paralysis and subsequent asphyxiation. 8 – 10 leaves could send you to your maker, though there is much variation according to season, stage of growth, location etc. The toxins are more concentrated in the roots and seeds.

Hemlock flower

Hemlock flower

For more information on this and other members of the carrot family see “Know Your Carrots” and my in depth article – “An Introduction to the Apiaceae Family for Foragers

For more discussion on toxic plants and fungi see “The Day I Ate a Deadly Plant: The Spectrum of Edibility

View more poisonous species


  • Joe says:

    Been doing your “Master Umbellifers in 2 Years” project and spotted hemlock this morning in Edinburgh. Never knowingly seen it before. Thoroughly delighted. I’ve been searching for it for years. Cheers, Mark!

    • mark says:

      Great, so glad its helping. weird how it feels better to find a really poisonous plant than a really tasty one! 🙂

  • Cameron says:

    Distribution seems to vary wildly for hemlock. Amazed to read that Joe above looked for years before finding it. I went for a walk in Bedfordshire this weekend and found it everywhere I looked. One footpath had non stop hemlock lining it for 2km or more.

  • Bex Powis says:

    Think I have some in the garden. Live on East Yorkshire coast. Is it OK as ornamental plant?

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