Source: RBG, Edinburgh
These subgenera can be basically divided into four groups:
The Rhododendron is the State Flower of Washington and West Virginia.
There are many hybrid varieties of Rhododendron. These have been bred to have larger or smaller flowers, and a vast array of petal colours.
Rhododendrons have a toxin called grayanotoxin in their pollen and nectar. People have been known to become ill from eating honey made by bees feeding on rhododendron and azalea flowers.