The Washington Poison Center has reportedly treated 10 people so far this year who have eaten poison-hemlock (Conium maculatum). Because not all incidents are reported, that might be only the tip of the iceberg, says Dr. Alexander Garrard, the center’s toxicologist and clinic managing director. Spring is the peak time for people to eat poison-hemlock, which they mistake for many edible and other deadly wild plants — most of which have similar-looking leaves, flowers, and seeds.

Poison-hemlock foliage
Poison-hemlock foliage.
In Washington, one person died in 1999 and another in 2010 after eating poison-hemlock. Anyone who has eaten poison-hemlock should immediately be taken to a hospital emergency room. Call the Washington Poison Center at 1-800-222-1222 for more information and assistance. All parts of poison-hemlock can kill humans and animals, even when it is dried. Foragers can easily mistake it for wild carrot (Queen Anne’s Lace), parsley, parsnip, sweet cicely, anise, fennel, wild chervil, and caraway, as well as other plants in the parsley or carrot family (Apiaceae), such as the violently toxic western-water-hemlock, or watercress, which is in another family. Toxic alkaloids in poison-hemlock affect the nervous system, causing such symptoms as a burning sensation in the mouth, nausea, vomiting, confusion, rapid heartbeat, seizures, and paralysis. Death is by respiratory paralysis. There is no antidote. Even touching the plant may cause a severe skin reaction in some people. “Misidentifying poison hemlock or other toxic plants can have truly tragic results,” says Alison Halpern, executive secretary of the Washington State Noxious Weed Control Board. “Learn from an expert before foraging for wild plants, and if you think you have poison hemlock on your property, contact your county weed board, conservation district, or WSU Extension office to learn how to safely get rid of it.”
Poison-Hemlock flowering
Poison-hemlock when flowering.
Widespread in Washington state, poison-hemlock aggressively invades roadsides, construction sites, vacant lots, streambanks, and gardens, especially where the soil is moist. It shows up as a weed in pastures and meadows. It can end up in hay or silage and poison animals. Poison-hemlock is difficult to distinguish from other plants in the carrot or parsley family. Telltale characteristics are purple spots on a smooth, hairless, hollow stem 2 to 12 feet tall and a musty smell some liken to mouse urine. Unrelated to hemlock trees, poison-hemlock spends its first year as a rosette of glossy, fernlike leaves. In this stage, its stem may or may not show purple. In spring its second year, it produces many umbrella-shaped clusters of white flowers, which develop into ridged seeds. In contrast, wild carrot (Daucus carota) has one dense flower cluster on a narrow, hairy stem, sometimes with one purple flower in the center, and is usually 3 feet tall or less. Poison-hemlock is a Class B noxious invasive weed. Its control is required in some counties in Washington, but removal is recommended everywhere to prevent accidental poisonings and to keep it from spreading onto other properties. Remove small patches by digging, making sure to remove the taproot. Don’t mow or cut plants as they will only re-sprout, and the cut plants can release toxic fumes. For larger patches, herbicides containing glyphosate can be effective, especially when the plant is a rosette in the spring. Don’t apply herbicides to mature plants because they will still set seed before they die. Herbicide treatments may need to be repeated as seeds in the soil germinate. To prevent contact poisoning, wear gloves, eye protection, a mask, and other protective clothing when removing poison-hemlock and surrounding soil. Never burn poison-hemlock, as the smoke can trigger asthma, and don’t leave plants where children or livestock might get them since the dried plants are just as poisonous. Never compost the plants, but put them in plastic bags and throw them in the trash.