Purple Nightshade (Atropa belladonna)
Why we grow it: Though rarely cultivated, the curvy, greenish-purple blooms are sometimes grown for their upright habit and eye-catching, shiny berries. Native to Europe, North Africa, and Western Asia, it has naturalized in parts of North America, favoring shady, moist locations with limestone-rich soils.
Deadly parts: The entire plant, particularly its berries, roots, and leaves.
Toxic toll: Don't mess with this one—pop a handful of berries in your mouth, and you'll physically be unable to call for help. After you lose your voice, respiratory complications, intense digestive disruption, and violent convulsions begin, the combination of which has proven fatal.
Photo by Flickr user peganum