Posion hemlock Belongs to the Parsley, Umbelliferae Family.

Despite the “hemlock” in its name it bears no relationship to the evergreen hemlock tree, Tsuga, L. It resembles many members of the family including Carrots, Parsley, Parsnips, and Queen Anne’s lace with:

•  rich aromatic volatile oils;

•  “compound umbels”, that is, all stems of flowers radiate from a single point at the tip of the stalk and in turn bear another umbrella of smaller stems with a multiplicity of tiny florets;

•  similar florets and seeds;

•  alternate leaves that “compound” (leaf with 2 or more leaflets) and re-compound “pinnately”, or like feathers around a quill, and that appear lacy or ferny;

•  hollow stems.

To Help Distinguish Poison hemlock from its Family:

•  It has hairless stalks with purple spots or streaks. Stalks grow as tall as 10’.

•  Poison hemlock’s flower clusters splay widely and grow atop each other in a less compact, tidy fashion than benign look-alikes, and resemble those on Spotted waterhemlock.

•  Leaflets become more ferny, divide more often and appear shorter and wider than those of toxic, Spotted waterhemlock, but separate more and appear less dense than those on Queen Anne’s lace.

•  Short, stout, white taproots with vigorous side branches resemble those of Parsnips. When crushed, roots emit intense scent from volatile oils: in young plants, the scent resembles that of Parsnips; in older plants, roots stink like musty mouse urine and provide a repugnant warning.

The poison in Poison hemlock, coniine works much like curare to cause a quiet neuromuscular paralysis. Coniine first paralyzes outer limbs, then the muscles of the lungs and heart, which then leads to coma and death. Poison hemlock contains five alkaloids which have varying toxicity levels that change with season and environment. One of its alkaloids, coniceine has 8 times more toxin than coniine and occurs more in the young plants, while coniine appears more commonly in seed and mature plants.

Pictures below contrast Wild carrot, a.k.a., Queen Anne’s lace, Daucus carota with Poison hemlock, Conium maculatum and Spotted waterhemlock, Cicuta maculata.

Left: *Queen Anne’s lace has larger fluffier closer leaflets Right: *Poison hemlock has shinier, more acutely cut leaflets splayed out wider

Above: *Spotted waterhemlock has longer, less divided, less ferny leaflets

*Leaf and Stem Photos courtesy of Dr. Andrew Senesac

Left: Queen Anne has hairy legs, i.e. stalks! No spots on stalks, shorter to 3’ Center: *Poison hemlock stalks grow smooth, spotted, and taller to 10’ Right: Spotted waterhemlock stalks grow smooth, streaky, and to 8’ tall

Poison hemlock arrived here from Europe either as a common folk-cure for cancer, one that probably eliminated cancers and life with it, or as the ornamental “Winter fern.” Maybe it works in its proper season or dose, but I’d hate to test it out. Herbalists used it as treatments for tumors, ulcers, gout, and as a sedative, anodyne and antispasmodic—though alternatively, it might well define a prime example of “the operation was a success, but the patient died”.

ANTIDOTE: Induce vomiting, apply “gastric lavage”, or pump the stomach, administer activated charcoal, and use artificial respiration if breathing stops. This helps in many cases of unknown source poisonings.

Spotted waterhemlock, Cicuta maculata, is the most toxic plant in North America and it’s a native. It and its cousin Poison hemlock, Conium maculatum, cause many of the fatalities due to misidentification of plants because both contain lethal poisons within a small dose, resemble edible plants, and grow in countless wetlands. Spotted waterhemlock originated here, it grows ONLY in wetlands, and exacts a more violent convulsive death than Poison hemlock. Its roots and stems contain the largest quantities of its most lethal toxin, cicutoxin. Cicutoxin causes violent central nervous system failure leading to painful salivating, vomiting, tremors, and convulsions, followed by asphyxiation. A big bite can kill adults, a nibble can kill children, one root or 8-10 ounces of mature plant can kill a cow or horse in 15 minutes to 3 hours, 2 ounces can kill a sheep, and I wouldn’t advise playing with dosage on cherished pets.

Even crushed parts can contaminate water! Furthermore, spraying with herbicides makes it more palatable to animals for 3 weeks thereafter, which makes this weed even more dangerous. Herbicides sprayed within 20 feet of a water table cause the most damage to the environment.