Eugene Weekly : Gardening : 6.11.2009


Scent of the Rogue
Native azaleas in bloom
by Rachel Foster

One of the highlights of a raft trip down the Rogue River a few years ago was the glorious sight and scent of native azaleas that covered some stretches of the river bank. The azalea was Rhododendron occidentale, a deciduous shrub that occurs in a coast-hugging strip from Santa Cruz county, California, to Coos County, Oregon, from sea level to 9000 feet. 

Western azalea is one of only three native rhododendron species that are found west of the Rocky Mountains. Pacific rhododendron (Rhododendron macrophyllum) is the most familiar. This big evergreen is plentiful in the coastal forests of Oregon and Washington and on the western slope of the Cascades. It is easy to grow and makes a nice addition to irrigated gardens. Cascade azalea (Rhododendron albiflorum) is hard to cultivate and seems scarce even in its native habitat. I’ve hiked the Cascades for years and have seen it only a handful of times. 

The gem among our three rhododendron species is Western azalea. Like many wild plants it is highly variable, growing from 3 to 15 feet in height and occasionally more. The flowers are generally white with a yellow blotch inside, but they are often tinged with pink or even red, and range in size from a little over an inch across to nearly 4 inches. This fabulously fragrant shrub has tempted hybridizers for 150 years, primarily in Europe, contributing its perfume to the famous Exbury line of deciduous azaleas and to hybrids such as ‘Irene Koster.’

Over the last century, here in the Northwest, a handful of collectors catalogued, selected and distributed some particularly fine forms of the species itself. Today these plants are relatively hard to find in nurseries, but Greer Gardens lists several varieties.

I have two plants I bought as babies from local plant sales. About 10 years on, they are less than 3 feet high, with modest but shapely flowers just shy of an inch and a half across. One has particularly colorful buds, with a strong pink flush and a distinct line of color along the outside of each petal. This is a striking occidentale feature that comes through in ‘Irene Koster.’

It’s a thrill to encounter Western azalea along the Rogue or in the Siskiyous. It is pretty darn nice in the garden, too, blooming quite late in the rhododendron season when most deciduous azaleas are over. Wild inland and mountain populations grow near streams, rivers and springs, indicating a liking for moisture. But it tolerates periods of dryness between waterings in summer, especially with some shade. It also tolerates soggy soil in winter, and the leaves seem to be less susceptible to the powdery mildew that often disfigures other deciduous azaleas by late summer. 

What is an azalea, anyway? Botanically speaking, all azaleas are rhododendrons, so what justifies calling them by another name? There are a number of features that separate azaleas from rhodies, although none seems to be completely reliable. The easiest to grasp is the number of stamens per flower: five in azaleas (occasionally six to 10), and 10 or more in rhododendrons. This works most of the time. Interestingly, the Cascade azalea I mentioned earlier is sometimes called ‘white rhododendron.’ How many stamens does it have? Ten. 

Rachel Foster of Eugene is a writer and garden consultant. She can be reached at rfoster at efn dot org