Deadly Nightshade
Unsurprisingly, the deadly nightshade plant is, well, deadly. Due to the alkaloids in its stems, leaves, berries, and roots, the plant is incredibly poisonous to human beings. Even rubbing up against it can cause irritation to the skin, according to the Royal Horticultural Society.
It would take just two berries from this plant to kill a child and between 10 and 20 to kill an adult.
