■ ­At the Rhododendron Species Botanic Garden (left), the large leaves of Rhododendron kesangiae (center) give dramatic contrast to the tiny leaves of Rhododendron keiskei ‘Yaku Fairy,’ the two low mounds below it (left of center). photo/PHIL WOOD
■ ­At the Rhododendron Species Botanic Garden (left), the large leaves of Rhododendron kesangiae (center) give dramatic contrast to the tiny leaves of Rhododendron keiskei ‘Yaku Fairy,’ the two low mounds below it (left of center). photo/PHIL WOOD
Almost everyone in the Northwest has a rhododendron in his or her garden. They are easy to grow and burst into spectacular bloom in the spring — probably outside your window as you read this.

They are so commonplace we overlook the value that they can bring to planting design. The gorgeous flowers thrill us for two weeks out of the year, but the evergreen foliage soldiers on the other 50 weeks.

A complementary plant
Rhododendron foliage is useful in planting design not only because it is evergreen but also because of the myriad choices in leaf size and shape. Foliage size varies enormously in rhododendrons, from one-half inch on the cultivar ‘Ramapo’ to more than 18 inches on the species Sinogrande.

Leaf shapes range from perfectly round to oval to linear. Rhododendrons can be used alone for planting design or contrasted with the foliage of other plants in the garden.

Rhododendrons vary in height, from 6 inches to tree size. Give the taller ones room to grow; pruning them to keep them small may remove the buds for next year’s bloom.

When creating a planting plan, consider flower color, too, even if it is fleeting. Many rhododendron plantings go terribly off-key at bloom time when too many different colors are all shouting at the same time.

In any given composition, be aware of time of bloom, and work with harmonious colors in that time frame. For a sophisticated composition, repeat colors in the rhododendron bloom with the colors of other companion plants, such as picking up the color of a yellow-blooming Rhododendron lutescens with the pale variegation of Euonymus ‘Moonshadow.’

Specific site conditions
Cultural considerations are very important when using rhododendrons in the garden. Know your site, and choose plants that will do well. Most large-leafed rhododendrons do best in part shade and won’t thrive in hot southern or western sun. An overhead canopy of conifers offers ideal conditions. For sunnier sites, choose rhododendrons with smaller leaves.

Rhododendrons are not low-water-use plants. Many species come from regions in Asia with ample summer rainfall. Expect to give them supplemental summer water once or twice a week. Most rhododendrons will droop when they need water, so they give a warning when they need a drink.

Established rhododendrons need less-frequent watering — look at all of the plants in old neighborhoods that have grown to great size with little attention. My garden came with an enormous ‘Cynthia’ rhododendron, at least 50 years old. Sitting on top of a rockery that gets little irrigation water, it never flags, no matter how dry the summer.

Rhododendrons are particular about where they grow. They like good drainage and won’t thrive in swampy, waterlogged soil. If you have such conditions, plant rhododendrons on mounds of well-draining soil.

Fine examples on view
Visit the Rhododendron Species Botanical Garden in Federal Way to see spectacular examples of species rhododendrons. Species rhododendrons are the progenitors of all the hybrids available today, the result of crossbreeding. Species offer a broader range of foliage texture than available in hybrids.

Most visitors to the garden go in April and May when the plants are in bloom; however, visiting other times of the year allows careful observation of the foliage.

The Rhododendron Species Botanical Garden is 22 acres of gardens that demonstrate artful combinations of rhododendrons and companion plants.

Part of the garden is nestled in the shade of tall conifers. The garden features a collection of ferns maintained by the Hardy Fern Foundation. The fine-textured ferns provide a good contrast to the bolder leaves of the rhododendrons.

Maples, magnolias, heathers, iris and primroses, along with other plants, add depth to the garden, too. The layered effect provides a good demonstration for gardeners who are dealing with shade from conifers.

The Rhododendron Species Foundation Botanical Garden is halfway between Seattle and Tacoma on the Weyerhaeuser Corporate Headquarters Campus at 2525 S. 336th St., in Federal Way. For directions, visit the website at www.rhodygarden.org or call (253) 838-4646.

In spring and summer, the garden is open from 10 a.m. to 4 p.m. six days a week through Aug. 31; it’s closed on Thursdays. From September through February, the garden is closed on Thursdays and Fridays. General admission is $5, seniors and students are $3 and children under 12 are free.

PHIL WOOD is the owner of Phil Wood Garden Design in Seattle and is a widely published freelance writer.