(This article is about plants named "hemlock." There is also a place in Michigan by that name: see Hemlock, Michigan.)

Several plants are called hemlock.

  • Poison hemlock is a common European plant, Conium maculatum, family Apiaceae (formerly Umbelliferae); it is toxic, containing the alkaloid Coniine.
  • Water hemlock is Cicuta virosa, another deadly plant in the Parsley family.

It is unknown which of above two toxic hemlocks the Greek philosopher Socrates drank to fulfil his execution sentence.

Quite different from these are the conifers

  • Western hemlock, Tsuga heterophylla. This is particularly common in the Pacific Northwest of North America.
  • Eastern hemlock Tsuga canadensis.
  • Mountain hemlock Tsuga martensiana.

Similar in appearance to hemlock is Queen Anne's Lace, with the exception that the latter features purpleish flowers in the center. Likewise, parsnip, of the carrot family, which is plucked, cut up, and boiled into soups and other dishes, has a white cluster of flowers and grows in similar places. Parsnip can be easily mistaken as hemlock and vice-versa. A good rule of thumb is that hemlock is more stalk-like. It is essential, of course, that one knows what one is picking, or the results could very well be deadly.

Hemlock, Queen Anne's Lace, and Parsnip commonly grow in ditches in most temperate regions of the globe.