water hemlock: see poison hemlock.

poison hemlock, lethally poisonous herbaceous plant (Conium maculatum) of the family Umbelliferae (parsley family). It has rank, finely divided foliage, flat-topped clusters of small white flowers, and a hollow, purple-mottled stem. Although native to the Old World, it is now naturalized and common in parts of the United States. The poisonous principle (the alkaloid coniine) causes paralysis, convulsions, and eventual death. Poison hemlock was used in ancient Greece in executions; a famous example was the philosopher Socrates. The related water hemlock (any species of Cicuta) is similar in appearance and as poisonous. C. maculata, called also musquash-root, spotted cowbane, and beaver poison, is the common species of E North America. The evergreen trees called hemlock are unrelated. Poison hemlock is classified in the division Magnoliophyta, class Magnoliopsida, order Apiales, family Umbelliferae.

hemlock, any tree of the genus Tsuga, coniferous evergreens of the family Pinaceae (pine family) native to North America and Asia. The common hemlock of E North America is T. canadensis, an ornamental tree (sometimes cultivated as a hedge) with small cones and short, dark green leaves so arranged as to give the branchlets a flattened appearance. The tree has been highly valued as a source of tanbark but is now seriously reduced in number. Its wood is soft and light. One of the two Western hemlocks (T. heterophylla, the tallest tree of the genus) has more valuable wood, which is used in construction work. The ground hemlock is a species of yew. The poison hemlock and water hemlock are herbs of the family Umbelliferae (carrot family) of the division Magnoliophyta. True hemlock is classified in the division Pinophyta, class Pinopsida, order Coniferales, family Pinaceae.

Any of several poisonous herbaceous plants of the parsley family, especially Conium maculatum, believed to be the plant that killed Socrates. It is now common in the U.S. as well as in Europe. A tall biennial, this plant has green stems spotted with red or purple, large compound leaves, and white flowers. Though the poison is concentrated in the seeds, the entire plant is dangerous to livestock when fresh. Despite their common name, poison hemlocks are not conifers (see hemlock). Water hemlocks (Cicuta species) are similar and also dangerous.

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Any of 10 species of coniferous evergreen trees that make up the genus Tsuga, in the pine family, native to North America and central and eastern Asia. Some are important timber trees, and many are popular ornamentals. Other plants commonly called hemlock include ground hemlock (see yew) and poison hemlock and water hemlock (parsley family). A true hemlock is a tall, pyramidal tree with purplish or reddish-brown bark, slender horizontal or drooping branches, and short, blunt leaves that grow from woody cushionlike structures on the twigs.

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