In this group

Flame AzaleaRhododendron calendulaceum

This native Appalachian shrub has yellow to orange or red flowers and blooms from late April into early July depending on elevation.

Swamp AzaleaRhododendron viscosum

This eastern native grows in moist sites and has fragrant white to pale pink flowers in summer.

Pinkshell AzaleaRhododendron vaseyi

This southern Appalachian native opens pink flowers before or with the new leaves in spring.

Korean RhododendronRhododendron mucronulatum

This Asian species is grown in cold-climate gardens and can open lavender-pink flowers before its leaves.

Rosebay RhododendronRhododendron maximum

This evergreen shrub is common in eastern U.S. mountains and has clusters of pale flowers.

Pacific RhododendronRhododendron macrophyllum

This native grows in forests of northwestern California, western Oregon, and Washington; pink flowers appear from May to July in Oregon and Washington.

Appearance

Growth form

The genus ranges from low shrubs to small trees. Some tropical species even grow on other trees without rooting in soil.

Flowers

Gardeners often call plants with about five or six stamens azaleas and those with ten or more stamens rhododendrons, but this is a useful rule of thumb rather than a clean scientific division.

Fruit

After flowering, many species form dry capsules that split and release numerous tiny seeds.

How to recognize it

Most are shrubs with simple leaves and showy funnel-, bell-, or tube-shaped flowers clustered near branch tips. Some are evergreen and leathery-leaved, while many azaleas are deciduous and have finer leaves.

Look-alikes

Where it lives

Typical habitats

• woodlands
• mountain slopes
• wetlands
• gardens

Range

Rhododendron is native across much of the temperate Northern Hemisphere, tropical Asian mountains, and northeastern Australia. In the United States, native species are especially diverse among the deciduous azaleas of the Southeast.

Preferred conditions

Many garden rhododendrons prefer acidic, well-drained soil that stays evenly moist. Sun, heat, and winter tolerance vary greatly among species and cultivars.

Life cycle

Seed dispersal

The small, light seeds are carried short distances by wind after the capsule opens.

Growing it

Propagation

Garden plants are propagated by seed, cuttings, layers, grafts, and tissue culture. The best method depends on the species or cultivar.

Toxicity

Many Rhododendron parts contain grayanotoxins. Leaves, flowers, or honey made mainly from their nectar can cause poisoning, so this group should not be treated as edible.

Connected species

Pollinators

In the eastern United States, some native azaleas attract butterflies and hummingbirds. Flower visitors differ by species and place.

Pollinators

• Eastern Tiger Swallowtail ComplexPapilio glaucus

  In the Appalachians, these large butterflies carry flame azalea pollen on their wings and are its most effective pollinators.

Name and classification

Group name

Rhododendrons and azaleas both belong to Rhododendron. “Azalea” is a garden name for several groups within the genus, not a separate genus.

Number of species

Worldwide, Rhododendron includes about 1,100 species. North America's deciduous azaleas include 15 species.

Varieties and forms

Thousands of named cultivars and hybrids differ in flower color, size, hardiness, and whether they keep their leaves. A garden photo may be identifiable only as Rhododendron or as a cultivar group.

Culture and stories

Culture and stories

• Native azaleas are valued in eastern U.S. woodland gardens for spring and summer flowers in white, pink, yellow, orange, and red.