2. Hydrangea
Hydrangea garden slug is a medium-sized bush with gorgeous blossoms. This plant’s petals come in many colors like pink, white, red, and blue-colored. The petals are long-lasting. All parts of the Hydrangea plant contain cyanide, which is one of the deadliest poisons known to man. As far as the poisonous nature of the plant is concerned then only the flower buds are harmful when consumed.