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Top 10 Most Poisonous Plants

Water Hemlock

The water hemlock, or cicuta maculata, is a very attractive wildflower with an upright growth pattern, purple-striped leaves and small white blooms. But the water hemlock's white roots are sometimes mistaken for a parsnip plant -- a potentially fatal error. The poison contained in the water hemlock, cicutoxin, is present in the entire plant, but is most concentrated in the roots. Anyone who confuses the plant with parsnips and decides to take a bite faces a violent death.

The water hemlock, which is native to North America, is considered by many to be the most deadly plant on the continent. The wildflower, which grows to 6 feet (1.8 meters), thrives along stream banks, in marshy areas, and in low-lying, damp meadows.

For those unlucky enough to taste the water hemlock, the onset of illness is rapid. The cicutoxin contained in the plant causes violent and painful convulsions, nausea, vomiting, cramps and muscle tremors. Those who survive the poisoning experience long-term health conditions, such as amnesia. No amount of water hemlock root is considered safe to ingest.