WSU Clark County Extension

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Irene Koster Western Azalea

Scientific name: Rhododendron occidentale 'Irene Koster'

Type:Deciduous shrubs
Plant Requirements
Zone:7 to 9
Sun:Full to partial sun
Plant Characteristics
Height:8 ft
Width:8 ft
Bloom:Fragrant flowers
Bloom Time:April to May
Bloom Color:Pink
Additional Characteristics



Wildlife value

Description Northwest outdoor enthusiasts love to stumble across wild stands of Western Azalea in the spring. This cultivar has been selected from the wild for its white to slightly rose colored flowers.

This deciduous shrub grows to 6’-10’ in both height and width. Leaves are 1”-3” long and elliptic in shape. They have a very nice shiny green color. In the fall before the leaves are shed for the season they will turn a range of colors from yellow to scarlet to crimson.

Flowers come on strong during April through late May. Upon flower inspection, one will find dark pink strips with a showy yellow blotch. Flowers have a pleasing fragrance as well. The more common Exbury Hybrids have larger flowers.

Look for a sight that receives full or partial sun. Enrich the site with plenty of organic matter to help mimic its life in the woods. It helps if the site is kept moist.

The usual suspects would include root weevils and aphids.
For assistance, contact Dr. Charles Brun (, (360) 397-6060 5701
Computing and Web Resources, PO Box 6234, Washington State University, Pullman WA 99164-6234