Poison Hemlock Identification: Stem Spots and Look-Alikes

Look at the stem first. Poison hemlock has a smooth, hairless, hollow stem marked with purple or red spots and streaks, and that combination is the feature King County's noxious weed program calls the one that sets it apart from its look-alikes. Then check the rest:

• Height. 6 to 10 feet in its second year (King County, NC State); Minnesota DNR gives 3 to 8 feet.
• Leaves. Bright to dark green, fern-like and finely divided with toothed edges, triangular in outline and 8 to 16 inches long, with stalks that clasp the stem (King County, Minnesota DNR). NC State notes they resemble parsley.
• Flowers. Tiny white five-petaled flowers in umbrella-shaped clusters 3 to 6 inches across, May to August (Minnesota DNR).
• Root. A single white, carrot-like taproot (King County). Penn State Extension gives about 10 inches.
• Smell. King County describes a strong musty odour when crushed; Minnesota DNR says crushed leaves and roots smell like parsnip or fennel. Do not crush the plant to test it with bare hands.
• Timing. A biennial: a low rosette in year one, then the tall flowering stalk in year two. King County says it comes up earlier than similar plants, in March and April, and seeds form by early August.

Feel the stem (with gloves) and look at the height.

• Stem. Poison hemlock: smooth, hairless, with purple spots or streaks. Queen Anne's lace (wild carrot, Daucus carota): NC State describes a bristly, hairy stem.
• Height. Poison hemlock reaches 6 to 10 feet; NC State gives Queen Anne's lace 2 to 4 feet.
• Flower head. Queen Anne's lace forms a lacy, flat-topped cluster 3 to 4 inches wide, blooming mid-summer to mid-fall (NC State). Poison hemlock's clusters are 3 to 6 inches across (Minnesota DNR). Size overlaps, so the flower alone does not settle it.
• The purple centre floret. Many guides use the single dark floret in the middle of Queen Anne's lace as the test. Do not rely on it: NC State's own poison hemlock profile also mentions a purple flower in the centre, and not every Queen Anne's lace head has one.

If any feature points to hemlock, treat the plant as hemlock.

Poison hemlock belongs to the carrot family, and its relatives include food plants and other dangerous weeds. The sources list:

• Edible plants and herbs: wild carrot, parsnip, parsley, anise, fennel and chervil (NC State, King County). This is why foraging for any wild carrot-family plant is risky.
• Other toxic or harmful plants: spotted water hemlock (Cicuta maculata), which NC State rates high severity with the roots the most poisonous part; and giant hogweed and rough chervil, which King County lists as look-alike noxious weeds.
• Harmless natives: sweet cicely, which Minnesota DNR lists as a look-alike.

Water hemlock can be told apart by leaf veins that end in the notches between the teeth rather than at the tips, and by hollow stems with cross-partitions at the nodes (NC State), but both hemlocks are deadly, so the distinction matters to botanists more than to anyone deciding whether to touch or eat a plant.

The serious danger is eating it; touching it can irritate skin. King County says that after touching poison hemlock, washing with soap and water is generally enough, but that the sap can cause a serious reaction in some people, who should seek medical help. NC State notes contact dermatitis in people with sensitive skin, and Penn State Extension calls the sap a skin irritant. Wear gloves, long sleeves and long trousers when handling it, and wash exposed skin afterwards.

Ingestion is a different matter. King County says eating even a small amount of any part can kill people, livestock and wildlife; NC State lists symptoms from salivation and vomiting to paralysis, convulsions and coma, caused by the alkaloid coniine. If someone may have eaten any part, or has a skin reaction that is spreading, call Poison Control at 1-800-222-1222 in the US or emergency services, and bring or photograph the plant.

Yes, especially where children, pets or livestock can reach it, and in some places it is required. King County lists it as a Class B noxious weed with control required on public lands and roads, and Minnesota lists it as a Prohibited Noxious Weed that may not be transported, propagated or sold. How to do it safely, according to those programs:

• Protect yourself. Gloves, long sleeves and long trousers (King County); wear protective gear with a string trimmer so plant material does not hit your skin (Penn State). King County adds a face mask when mowing.
• Pull or dig the whole root when the soil is moist in spring or fall (King County); Minnesota DNR says cutting the taproot 1 to 2 inches below ground also works. Penn State advises against hand removal of large plants because of the tough roots and irritating sap.
• Act before seed. Mow or cut flowering stems before seeds form (Minnesota DNR); one plant can produce over 30,000 seeds. Penn State says treating first-year rosettes is the most effective approach.
• Herbicides named by these programs include glyphosate, triclopyr and 2,4-D; follow the product label and local rules.
• Disposal. Bag it and put it in the regular trash (King County). Do not compost it and do not burn it: Minnesota DNR says the toxins persist, including in compost, and burning can release them into the air.

Hemlock trees are a different plant entirely. The eastern hemlock (Tsuga canadensis) is a conifer that NC State describes with small, glossy needles about half an inch long, two pale bands on the underside of each needle, and brown oval cones about three-quarters of an inch long, on a tree 40 to 70 feet tall. NC State lists it as non-toxic to cats, dogs and horses. It shares only the English name with poison hemlock (Conium maculatum), which is a herbaceous weed, not a tree.

Photograph the stem close up (spots and surface), a leaf, and the flower head, from a safe distance or with gloves on. A plant ID app can tell you whether the plant is in the carrot family and which species it most resembles. For a plant you plan to remove, that is enough to decide to treat it as hemlock. For any plan to eat a wild carrot-family plant, an app result is not enough and neither is this page: do not eat it. Your county extension office or noxious weed program can confirm a plant from a sample or photo.

Research and drafting for this page were done with the help of AI, and every figure was then checked line by line against the sources listed at the end of the page. Sources were opened on 2026-09-25. If you find a mistake, tell us and we will correct it.