Poison Hemlock

Although many members of the carrot/parsley family are edible and have medicinal uses, as I mentioned in my most recent post about desert parsley, other members of this group are highly toxic. Many of these related species have fern or carrot-like leaves, taproots, five-petaled flowers and seeds that look very similar. For this reason extreme care must always be taken to properly and unequivocally identify these plants before ingesting them.

With its leaves that resemble parsley and its seeds that can be mistaken for anise, poison hemlock (Conium maculaum) is perhaps one of the best known plants that is confused with edible carrot/parsley family members. All parts of the poison hemlock plant are extremely poisonous because of the alkaloids they contain! Eating small amounts can can cause vomiting, convulsions, difficulty in breathing and coma. Symptoms can be caused by such a small amount of the poison hemlock alkaloids that hand washing after touching the plant is suggested. Ingested in quantity poison hemlock can be fatal. Supposedly it was with a draught of poison hemlock that Socrates killed himself in 399 BC. Animals will usually avoid eating poison hemlock unless forced to do so because of food scarcity – with disastrous results.

A non-native biennial introduced from Europe, poison hemlock is a giant plant that can grow to ten feet in height. It is now established throughout all of the contiguous United States except Mississippi and Florida as well as most of Canada. Common in disturbed places, poison hemlock can form dense stands. It can tolerate poorly drained soil and is often found along stream and ditch banks.  When Poison hemlock invades pastures, vineyards, orchards and fields it is considered a noxious weed.

Poison hemlock has a single , extensively branched, hollow stem that  grows from a fleshy white taproot. Characteristically the stem is usually spotted purple. The fern-like leaves are divided two or three times into deeply lobed or tooth-like segments. The lower leaves have short stalks that are flattened at the base and envelop the stem.  Upper leaves are stalkless or have very short stalks. The foliage gives off a musty odor. Numerous small white flowers are borne in loose umbrella shaped clusters. The flowers have five petals, no sepals and short stalks. The fruit is a flattened oval with longitudinal ribs containing two grey-brown seeds.

Hemlock parsley, snakeweed, and poison parsley are a few of the other common names for C. maculatum.

The word hemlock comes from two Old English words meaning “straw” and “plant” and was originally applied to members of the carrot/parsley with hollow stems.

These poison hemlock plants were photographed near the Tule River (Shasta County CA) but can be found throughout where we live in Northeastern California.

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1 Response to Poison Hemlock

  1. Pingback: Western Sweet Cicely | The Nature Niche

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