Water Hemlock/Spotted Parsley (Cicuta maculata)
Why we grow it: An unintended by not uncommon garden trespasser—with its small, white flowers growing in umbrella-like clusters—this perennial doesn't look too menacing. It may be growing on the edges of your property, especially if you live near a meadow, pasture, or stream.
Deadly parts: The whole plant, especially the roots of early growth.
Toxic toll: This wildflower has been dubbed "the most violently toxic plant that grows in North America" by the USDA. True to its killer reputation, water hemlock can strike you dead within 15 minutes of ingestion. The poison cicutoxin wastes no time in attacking the central nervous system, causing severe seizures and convulsions that turn deadly as a result of asphyxia and cardiovascular collapse.