There have been several articles written about Rhododendron occidentale, our Western Azalea. In this article I will focus on Stagecoach Hill, one of the richest sites for diversity or 'sports' among this group of plants. Located just above Highway 101 and Big Lagoon in Humboldt County, California, this extensive collection of the Western Azalea is visited by many interested botanists and other enthusiasts, especially in June when in bloom. Below is an old photograph by Frank Mossman of Stagecoach Hill above Big Lagoon.
The Western Azalea, R. occidentale is native to California, Southwestern Oregon and Mexico. It has been found that areas with the largest numbers of these plants have soil with high concentrations of the mineral Serpentine, which can be found on the hill in outcroppings and along the beaches near Stagecoach Hill. The two-mile-long hillside of azaleas was given the name "Stagecoach Hill" because of a road the old stagecoach used, until the early 1900's, that goes along this ridge. The Western Azalea, R. occidentale, is a deciduous shrub growing to 12 ft tall and wide, has lovely fragrant flowers of pink, white and yellow displayed from late May into July, and often found near streams or wet areas. The fragrance is most potent on warm, still afternoons and is compared to honeysuckle or nutmeg in aroma.
Photographing the Western Azalea is best done on a cloudy or foggy day in mid June. This way the shadows are reduced and the colors enhanced. A macro lens is useful as well as a wide angle/zoom lens. Here I am with Tim Walsh another azalea enthusiast and member of the Eureka Chapter of the Rhododendron Society on one of our field trips.
Going To Stagecoach Hill - Let's take a Hike
If one were to turn off of Highway 101 going east on Kane road and stay to the left at each junction, you will eventually come to a shady wide area with a sign that says "trail". If we take a hike on this trail, we find it goes through a climax spruce forest that has very little growing under. If it were late autumn there would be many patches of mushrooms to be found here. But now, on this day in mid-June, it is just a thick carpet of spruce needles. Ahead the trail leads us toward the west where we can see a bright area leading us out of the forest. As the trail breaks out of the darker forest, we start to see Western Azaleas with their colorful flowers. The plants closest to the forest, due to the lower light levels have the fewest flowers, but sometimes they are unique so we must check them out. The trail leads out into a wide expanse of the azaleas in full sun exposure, many shoulder height, but larger clumps are 12 -15 ft tall.
The view is spectacular with Big Lagoon in the foreground and the Pacific Ocean in the background. Small sailboats and some windsurfers can be seen on the lagoon. The day is warm and the air is perfumed by these special plants. It has been found that R. occidentale has 78 chromosomes, while all other American deciduous azaleas only have 26-54, depending on the cultivar. This may be what contributes to this plant having so many variations in foliage and flowers. It is these 'sports' that creates so much excitement for rhododendron enthusiasts who come here. When one looks across this wide expanse of blooming azaleas, it may appear that they are all the same, but upon closer inspection we see many differences.
Some have almost pure white flowers with a bright yellow flare in the upper lobe, while others have a bright magenta picotee edge on each white flower with a yellow throat as well. Some even have frilly edges giving them an exotic flair. As you hike along the trail and see plants with unique colors, you may find yourself going through the native brush for a closer look. It is a good idea to wear heavy leather gloves as sometimes the blackberry vines hold you back from the elusive flowers. Be sure to wear thick pants and sturdy boots for this hike. You may also want to bring your bug repellent as mosquitoes and ticks are common inhabitants in the tall brush.
Frank Mossman along with Britt Smith documented many variations of the Western Azalea along the Pacific Coast. Here are some they found. (Photos above by Frank Mossman)
Some variations of the Western Azalea found on Stagecoach Hill
1. The flower size is normally 2-3 inches in diameter, but some are as large as 4 inches
2. The petal shapes narrow to wide and some overlapping. Frilled margins and textures from smooth to crinkled
3. Petal number, or lobes, vary from 5 to 12
4. Stamen numbers are normally 5, but can be as many as 12
5. Flower color: white, cream, pink, deep pink, or red. The colors may be com¬bined in various ways with stripes and spots of one color or another; upper petal color yel¬low or orange, may be spotty, or splashed, or entire, and may extend to adjacent petals, or, rarely, to all petals. White or pink flowers may have red mar¬gins (picotee).
6. Flowers per truss: most common is 15-25, but up to 54 have been found
7. Leaf shape and color: quite a variety have been found from very narrow to almost round, color usually green, but often plum-colored or spotted; sometimes bronzy or even variegated.
8. Growth habit: Usually upright and spreading, but true dwarfs have been found
In the recent past, Dr. Frank Mossman (above) and Britt Smith spent years collecting some of the most unusual forms of this important species, sending many of them to collectors in Britain, New Zealand, Australia, Canada and Japan. These forms all have an 'SM' prefix code (except those that have been named), which stands for Smith Mossman, and many are out there being duplicated for gardeners.
Az. 'Humboldt Picotee' is one of the most sought after forms of the Western Azalea. The Eureka Chapter of the Rhododendron Society will have this variety available at their plant sale during the ARS National Spring Conference in Eureka, 2017. Dr. Mossman used some of these sports to create new hybrids for the American market. One such hybrid, 'Washington State Centennial' looks like a much larger flower truss of some of the most colorful forms. It is possible that other hybridizers around the world are using some of these interesting forms of R. occidentale to create other fabulous new azaleas. (Mossman 1975)
Distribution and Habitat
Many pockets of R. occidentale are found along the Pacific coast. In Oregon, Coos, Curry, Douglas, Josephine and Jackson Counties have the most colonies and plants and a few are found in Klamath County. Going south into California there are a considerable number of colonies in Del Norte, Humboldt, Siskiyou and Shasta Counties in northern California. Sonoma County and the Mt. Tamalpais area in Marin County also have some good stands. Plants are found in the Sierra Nevada Mountains often at an altitude from 6000 to over 9000 feet. Perhaps one of the best known colonies in this area is that in Yosemite Park where the plants line the banks of the Yosemite River often to the near exclusion of all other shrubs. Going south there are no reports of any until Riverside County where a considerable population occurs in the San Jacinto Mountains. Plants have also been found in the highlands of San Diego County which borders on Mexico, but these populations are limited to moist areas with springs. (Breakey 1960).
Rhododendron occidentale grows in acidic soils rich with organic material, and with ample water. Often found near streams or in low wet places tells us that it likes plenty of moisture, and since it is found in areas near the coast that are often foggy, moist air is also a preference. It can be found farther inland in higher elevations where heat is common, but these plants are most often growing in wet places. This tells us that the Western Azalea can take quite a bit of heat in summer as long as it is kept moist. Some plants, especially in southern California, tolerate alkaline soils, thus making the Western Azalea a good pick for those southern areas with alkaline water and soils.
Growing the Western Azalea, provided you live in an area that can support other rhododendrons and deciduous azaleas, is fairly easy. Given the requirements of a moist acid soil high in organic material, you will have great success. The plants grow fairly quickly and with little care. Some pruning over time will result in better specimens.