Azaleas are flowering shrub

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

s comprising two of the eight subgenera of the genus Rhododendron

Rhododendron

Rhododendron is a genus of over 1 000 species of woody plants in the heath family, most with showy flowers...

, Pentanthera (deciduous) and Tsutsuji (evergreen). Azaleas bloom in spring, their flowers often lasting several weeks. Shade tolerant, they prefer living near or under trees.
Azaleas differ from rhododendrons in being generally smaller and having one blossom per stem rather than blossom clusters.

Plant enthusiasts have selectively bred azaleas for hundreds of years.