For diversity of size, form, foliage and flower color, it is hard to imagine any other group of plants matching rhododendrons and azaleas. We all know about the spectacular garden hybrids with their blinding colors and huge flower heads. But there is another remarkable group known as species rhododendrons, wild plants found growing naturally in the forests and mountains of the world, many of which make outstanding garden plants. One of the best places to see them is the Rhododendron Species Botanical Garden in Federal Way, Washington, which contains one of the largest collections of rhododendrons worldwide.
Appeal: Thousands of variations with a virtually unlimited palette of floral color blooming from late winter into late summer. Some types are fragrant. The foliage of many species is extremely unusual and attractive, providing year-round interest.
The Rhododendron Species Botanical Garden in Federal Way, Washington, contains one of the largest collections of rhododendrons worldwide.
Zones: Easy to grow in cool-summer/mild-winter regions, Zones 5 to 9. Outside of these regions, it is still possible to grow many kinds if care is taken to select the appropriate cultivars or species. The RSBG is considered Zone 8.
Exposure: In general, rhododendrons require a bright but not-too-hot exposure with low soil temperatures. Exceptions are the tiny-leaved alpine and dwarf species, which are best in bright sun.
Soil: Excellent drainage in an organic woodland soil or in a sandy soil that has been amended with bark or other organic matter. In heavier and clay soils, plant in raised beds.
Care: Water through dry periods. Regular mulching with organic material means extra fertilizer is usually unnecessary. If the plants seem unhealthy, it is usually because of poor drainage.
DESIGNING WITH RHODIES
 Think mobility. Because of their fibrous root system, rhodies are easily moved as conditions warrant.
 Grow with ferns and wildflowers, which appreciate the light shade under rhodies.
 Plan for a long season. It’s possible to have species rhododendrons in flower from the earliest thaw of spring to the longest days of summer.
 Fit rhodies to the space you have. Most can be selectively pruned to reduce their size. Better yet, select the right-sized or even dwarf plant for the site.
 The subtle coloring of species rhododendrons is easier to integrate into the garden than the often harsh colors of hybrids.