Our omnipresent rhododendron does it all, all year round

Almost everyone in the Northwest has a rhododendron in the garden. They are easy to grow, most kinds are not rare or expensive and they burst into spectacular bloom in the spring. They are so commonplace, we overlook the value 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.

Rhododendron foliage is useful in planting design not only because it is evergreen but because of all the choices in leaf size and shape. Leaf size varies enormously in rhododendrons, from ½-inch on the cultivar 'Ramapo' to more than 18 inches on the species Sinogrande. Leaf shapes vary, too, from perfectly round to oval to linear. Rhododendrons can be used alone or contrasted with the foliage of other plants in the garden. Leaf color is a consideration, too; the cultivar 'PJM' turns mahogany in winter.

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 awry 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.'

Cultural considerations are just as important when using rhododendrons in the garden as when using other plants. Know your site, and choose plants that will do well on it. 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 Asia, from regions 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. Established rhododendrons need less-frequent watering — observe all of the large plants in old neighborhoods that have grown to great size with little attention. My garden, for example, 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.

Visit the Rhododendron Species Botanical Garden in Federal Way (www.rhodygarden.org) 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 hybrids. Most visitors to the garden come 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 comprises 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. The layered effect provides a good demonstration for gardeners who are dealing with shade from conifers.

Another part of the garden features a collection of alpine rhododendrons growing on a sunny slope. These are small-leafed, low-growing forms that do well in exposed locations.

Phil Wood has a degree in landscape architecture and designs and builds gardens. Write to him at thegardendesigner@seattletimes.com. Sorry, no personal replies.