The Greek philosopher Socrates is famed for being sentenced to death by drinking poison hemlock tea. So you should have a pretty good idea that ingesting hemlock isn't the smartest idea. The herbaceous plant, which is a member of the parsley family, is a tall biennial with a thick taproot and purple-spotted stems. It produces clusters of small, white flowers. Its leaves are often mistaken for wild parsley and its roots for parsnips.
While it's dangerous to consume any part of the plant, the deadliest section is the seeds, which contain coniine, a toxic alkaloid. Although poison hemlock is native to Eurasia, it was introduced to North America and is now found along its waterways and disturbed sites, much like common weeds.
So what happens if you eat this plant? You'll likely have the typical poisoning symptoms, such as vomiting, weakness and trembling. But hemlock poisoning also depresses the central nervous system and can put you in a coma. If you're unfortunate like Socrates, it can also kill you [sources: Encyclopaedia Brittanica, Weed Science Society of America].