Poison Hemlock Conium maculatum

Poison hemlock is a biennial, herbaceous weed in the carrot family (Apiaceae). It is native to Europe and the Mediterranean but has naturalized in the United States and become problematic. It is highly toxic and can be fatal to people and livestock. Many states have listed it as a noxious weed. 

It grows 6 to 10 feet tall and 4 to 5 feet wide and quickly colonizes an area and displaces native plant species. Its white fleshy taproot has red spots and resembles a parsnip or carrot. The stems are hollow and have small purple spots. Showy white flowers look like umbrellas or like other members of the carrot family. The leaves of poison hemlock resemble parsley. The roots, leaves and stems have a foul odor when crushed.

It is found growing in disturbed areas, at roadsides, along fences, on streambanks or in ditches. In early spring it emerges from the soil with a basal rosette of fine-textured ferny leaves. While it is usually a biennial, in ideal locations – full sun to partial shade and moist soils – it can be perennial. It reproduces by seeds which are dispersed by animals, machinery and clothing and persist in the soil for years, making eradication difficult.

Insects, Diseases and Other Plant Problems: No significant problems.