Western azaleas are tough for home gardeners, but Lake Wilderness Arboretum offers abundant blooms and bouquet

WESTERN AZALEA (Rhododendron occidentale) is a spring jewel with glistening blossoms and an intoxicating fragrance. The plant is native to Southern Oregon and into Northern California along the coast and at higher elevations, where the plants’ roots have access to consistent moisture and cool soil conditions. However, western azalea can be challenging in the home garden. 

Fortunately, Lake Wilderness Arboretum (lakewildernessarboretum.org) in Maple Valley is home to one of the largest collections of western azaleas in the world, and peak bloom season is right around the corner. The Arboretum, formerly known as South King County Arboretum, sits on 40 acres of mostly wooded land, with 20 acres of tended gardens, including the Smith-Mossman Western Azalea Garden. 

Britt Smith and Frank Mossman were plant collectors with a passion for native West Coast azaleas who spent years exploring hillsides and coastal regions studying the diversity of the species in the wild. Over the course of 15 years, the men discovered and documented about 275 unique forms of western azalea. The best of their collections found a forever home when Smith donated his fully grown plants to the Arboretum about 20 years ago.

The Smith-Mossman Western Azalea Garden was dedicated in 2000. In 2008, the garden was redesigned to include a variety of Pacific Northwest native plants to create the perfect setting to showcase the collection. 

Western azaleas are deciduous, with fresh green foliage emerging in spring on a vase-shaped shrubby framework to 4 feet tall and as wide. Somewhat gangly in youth (aren’t we all), mature shrubs retain an elegant grace, unlike their sometimes-stolid evergreen kin. 

In May and June, large clusters of trumpet-shaped blooms appear at the end of each branch, surrounded by a ruff of young leaves. 

Blossoms can be pure white to deep rose, often with yellow and orange markings, creating a range of delicious sherbet hues. Some blooms have frilled petals, crinkled like a crinoline. Others have a darker reverse to the petals for a dramatic two-toned effect. The fragrance is described as sweet and spicy — like clove pinks or carnations. Select plants, known as chimeras, produce blooms of varying colors depending on the age of the wood the flower is borne on. 

With so many charms, it’s easy to understand why gardeners would want to include western azalea in their home gardens. Yet, disappointing slow growth and persistent late-summer mildew that tarnishes the plant’s colorful autumn foliar display is not uncommon. The key to success is to provide conditions that emulate those found in the wild where native populations are thriving — namely, regular moisture, acid soil and cool roots. In the garden, a deep mulch shades roots, keeping them cool, and soil that’s rich in organic matter helps retain moisture. 

Address mildew problems by placing plants where breezes are constantly circulating. Avoid planting beneath eaves or up against a wall, where air tends to pool, or in crowded mixed plantings. While plants will tolerate light shade, you’ll get the best bloom in partial sun. Plan your visit to Lake Wilderness Arboretum to catch western azalea bloom season in all its glory, and see for yourself what ideal conditions look like — just follow your nose.