A very weedy biennial from a white taproot. The leaves divided into many small segments and the stem covered with purple blotches. This species often forms dense stands, over 6 feet tall, along stream courses but can grow in a variety of sites. The white flowers are in small, umbrella-shaped clusters, and the whole plant emits a musty `mouse nest`-like odor. This is the same species which killed Socrates, and human poisoning is common.