Rhododendrons contain poisonous substances and should not be ingested by humans or pets. Honey made from flowers may also be toxic. However, the flowers are visited for nectar by a variety of spring bees, including bumble bee queens, without any harm to these pollinators. The genus Rhododendron includes two major subgenera that are comprised of species known commonly as azaleas.

 

Native Regions

Eastern regions of the United States and Canada, the Pacific Northwest and California

 

Availability

Most Rhododendron species require moist, acidic, well-drained soils to flourish. Some species require several hours of sun for maximum flower production, but most do best in part shade to shade conditions. Numerous native species and ornamental cultivars are widely available in nurseries throughout North America.

 

Duration

Perennial

 

Bloom Time

Spring to early summer

 

Average Height

8 feet

 

Flower Color

Pink

White

Purple

Yellow

Red

Orange

 

Exposure

Partial sun to shade

 

Water Requirements

Moist to average

 

Recommended Species

Rhododendron arborescens (smooth azalea) is a large shrub, 8-12 feet in height, native to mountain bogs and stream banks of the eastern-most United States, from New York, south to Georgia. It produces fragrant, funnel-shaped, white or pink-tinged flowers with protruding, red stamens in late spring to early summer. It is one of the hardiest, fastest growing, native white azaleas. This commercially available species requires partially shaded, moist garden conditions.

 

Rhododendron prinophyllum (early azalea) is a 6-12 foot tall native shrub that produces funnel-shaped, light pink or purplish flowers in early spring. It occurs naturally in damp thickets, open wood and shores in the eastern part of the United States. This attractive azalea is extremely hardy and is commercially available. It requires moist, well-drained, acidic soil and shaded conditions.

 

Rhododendron macrophyllium (Pacific Rhododendron) is a 5-25 foot tall plant, native to the west coast of North America, from British Columbia south to northern California. Pacific Rhododendron occurs naturally in drier forest environments in Washington, where it is the state flower, and in wetter forest regions of northern California. The plant is most abundant in Oregon, where masses of pink blossoms provide a brilliant show in late spring and early summer. The individual flowers are bell-shaped and range in color from pink to deep rose-purple. This commercially available plant is the showiest flowering native shrub in the forests of western North America. It requires part-shade to shaded conditions, but can tolerate somewhat drier soils than other Rhododendron species.

 

Rhododendron occidentale (Western azalea), which is native to California and Oregon, is a fragrant, loosely branched, spreading shrub that is generally 3-9 feet tall. It produces large, white to deep pink, very fragrant flowers in large clusters at the stem ends. Variations in flower color can occur for this plant, which include mixtures of pale pink, deep pink and yellow-orange. Bloom time varies from spring to summer, depending upon region and elevation. It occurs naturally along stream banks and other moist places below 7500 feet and is a larval host plant for the hoary comma (Polygonia gracilis) butterfly. As a commercially available garden plant, it prefers part-shade and acidic, moist, well-drained soil.