Water Hemlock Identification: Leaf Veins, Chambered Roots

Water hemlock is identified by looking, not handling. The USDA Forest Service calls it the most poisonous plant in the North Temperate Zone, with all parts toxic and the roots worst. Wikipedia notes that ingestion in any quantity can poison and very small amounts can kill, and records a family who rubbed the plant on their skin and were poisoned, two children fatally. Wear gloves if you must touch it, and never taste any white-flowered plant in the carrot family to identify it.

If anyone may have swallowed part of it, call 911 at once if they collapse, have a seizure, have trouble breathing or cannot be woken; otherwise call Poison Control at 1-800-222-1222 or use webPOISONCONTROL online, and do not make them vomit (Poison Control, poison.org).

The single most reliable sign is in the leaflets. In most carrot-family plants the side veins run out to the tips of the teeth. In water hemlock they run to the notches between the teeth: the Forest Service describes veins that fork near the edge, one branch reaching the leaflet tip and the other ending in the V-shaped notch between lobes, and Wikipedia calls this unique in the family.

To see it without handling the plant, photograph a leaflet against the sky or with light behind it, so the veins show through. The leaves overall are two or three times divided, 30 to 90 cm long, with lance-shaped, sharply toothed leaflets (Wikipedia).

Water hemlock has a large swelling at the base of the stem (Wikipedia), and when the lower stem and upper root are sliced lengthwise they show a series of hollow chambers separated by cross-walls (USDA Forest Service). The tuberous roots hold a yellowish oily liquid that turns reddish brown in air (Wikipedia); To Know the Land describes the white rootlets as carrot-like.

This is the most toxic part of the plant, so we do not recommend cutting it to check. If a positive identification matters (for example in a pasture), ask your county extension office or noxious weed program to look at it.

Both are deadly carrot-family plants with white umbrella-shaped flower clusters, and both are called hemlock, so they are confused constantly. The differences from the sources:

• Roots: water hemlock has a branched cluster of tuberous roots; poison hemlock has a single taproot (Wikipedia).
• Stem base: water hemlock's base is swollen and chambered (Wikipedia; USDA Forest Service).
• Leaves: water hemlock has lance-shaped, sharply toothed leaflets with veins ending in the notches; poison hemlock has bright green, finely divided, fern-like leaves resembling parsley or carrot tops (see our poison hemlock identification page).
• Stem marks: poison hemlock's stem is smooth, hollow and blotched with purple or red; water hemlock's can also be purple-spotted (To Know the Land), so spots alone do not settle it.
• Where it grows: water hemlock is a plant of wet ground: ditches, stream banks, pond edges and marshes (USDA Forest Service).

Western water hemlock (C. douglasii) is the species in the northwestern U.S. and western Canada; the same genus features apply (USDA Forest Service; Wikipedia).

To Know the Land lists several look-alikes and how to tell them apart:

• Wild carrot (Daucus carota): a denser flower cluster, often with a dark purple flower in the center, hairy stems, and drier sites.
• Water parsnip (Sium suave): leaves divided only once, not two or three times (confirmed by Wikipedia).
• Angelica: much larger leaves and globe-like flower heads.
• Common beggarticks (Bidens frondosa): opposite leaf branching and yellow flowers.
• Poison hemlock: see the section above.

The same author points out that people are poisoned precisely because some of these relatives are foraged. Our position: no page or app photo is enough to decide that a white-umbel plant is harmless. Leave the whole group alone unless an expert has examined the actual plant in person.

The documented danger is mainly from swallowing it: symptoms such as nausea, vomiting, abdominal pain, delirium and seizures can begin within 15 to 60 minutes (USDA Forest Service; Wikipedia). Skin exposure is not harmless, though: Wikipedia records a fatal poisoning in which a family rubbed the plant on their skin, and the root's oily yellow liquid is the most concentrated source of the toxin (To Know the Land).

If the plant or its sap touches skin, Poison Control's first aid is to remove contaminated clothing, rinse the skin under room-temperature running water for at least 15 minutes, then call 1-800-222-1222 for advice (poison.org). Wash your hands before eating, drinking or touching your face.

Where children, pets or livestock use the area, removal is worth considering. The author of To Know the Land digs up individual plants found where small children are likely to encounter them. If you do it yourself, our advice is gloves, long sleeves and eye protection, removing the whole root, bagging everything, and washing up afterward. Near water or on a large patch, call your county noxious weed program or extension office first; they can confirm the identification and advise on local rules.

Without touching the plant, take: a leaflet with light behind it so the veins show; the whole leaf to show how many times it divides; the flower cluster; the lower stem where it meets the ground; and the wet habitat around it. NatureLens can suggest a species from these photos. For any white-umbel plant, treat the result as a reason to keep your distance, not as permission.

Research and drafting for this page used AI assistance. Every number, date and claim was then checked against the sources listed below, which were opened and read on 2026-09-25. Where a statement is our own advice rather than a sourced fact, the text says so.