Plant of the Week
Western Azalea (Rhododendron occidentale (Torr. & A. Gray) A. Gray)
By Russell Holmes
Western azalea is in the Ericaceae (Heath Family) which contains approximately 65 genera and over 1400 species. Species in the Heath Family are widely distributed ranging from deserts to high elevation tropic environments. Commercially, the family is important for a number of popular ornamentals and for blueberries and cranberries. Western azalea is widely cultivated and is one of the most attractive and aromatic of all of the azaleas.
Western azalea is a deciduous shrub 1 to 5 m (3.2 to 16.4 feet) tall. Leaves are bright yellow green, generally elliptic in shape, 3 to 9 cm (1.2 to 3.5 inches) in length and 1 to 3 cm (0.4 to 1.2 inches) broad. Flowers grow in clusters (corymbs) of 5 to 20 and are typically very fragrant, at times detectable from over a 100 meters distance. Individual flowers are irregular with a 2 to 3 cm (0.8 to 1.2 inches) tube and spreading undulate lobes that have an approximate equal length to the tube. Petals are glandular pubescent on the outer surface and are white to pink in color with a yellow stripe. Some forms have a yellow blotch on one of the petals.
The distribution of western azalea is restricted to an area west of the Sierra Nevada and Cascade Mountains from Mt Palomar in southern California north to the Umpqua Valley of southwest Oregon. It usually grows in wetland or riparian habitats but not in areas where its roots would be submerged in water. It is tolerant of serpentine soils and is often a component of the unique plant communities found growing in this soil type in southwest Oregon.
Explorers to western North America discovered this attractive plant in the nineteenth century. William Lobb sent seed to the Veitch Nursery in England in 1850. Since that time, it has become a popular landscape and garden plant and azalea enthusiasts have continued to search for unusual forms for both cultivation and science.