Rhododendrons are sometimes called the King of Shrubs because these flowering evergreen plants thrive in temperate landscapes. Large and leathery-leafed, rhododendrons sport pretty clusters of red, white, pink or purple flowers. Unfortunately for those looking for a snack in the wild, every bit of a rhododendron is toxic. The leaves in particular are dangerous. Chomping on some rhododendron can lead to stomach irritation and abdominal pain. Even worse, it might cause an abnormal heart rate, convulsions, coma and perhaps death [source: The Flower Expert].
Interestingly, those who have become sick from rhododendron poisoning usually have eaten honey crafted from the plant's nectar. Such rhododendron poisoning occurred as long ago as 400 B.C.E., when written records mentioned a "honey intoxication" that sickened 10,000 Greek soldiers who had eaten honey made from rhododendron nectar.
The plant is toxic to other animals as well; some dub rhododendron "lambkill" and "calfkill" because these young animals are unaware of its dangers, and sometimes perish after eating large quantities of leaves or flowers [source: Hoyum].