GARDENER'S JOURNAL: A rhododendron for every garden

Few garden plants are as popular and so widely used in New England landscapes as rhododendrons, and rightfully so. Our climate and soils are well suited for this group of plants, and most of those hardy in this region are easy to grow and relatively maintenance free. Many also retain their leaves during the dormant seasons, adding interest to winter gardens. Few gardens look complete without rhododendrons.

The rhododendrons that grow in this region can be classified into two groups: large leaf types and those with small leaves. (Note: although azaleas are technically rhododendrons, I will discuss them at another time.)

The name rhododendron is derived from the Greek words rhodos (meaning "rose") and dendron, ("tree"). In New England, rhododendrons rarely attain the stature of trees, and many are even well suited for smaller gardens.

In general, it is the large leaf types that grow very large here (8 feet high or more), and these are the ones most people recognize as rhododendrons.

Large leaf rhododendrons tend to come into bloom starting as early as late April, and the later flowering types (maximum hybrids) can be flowering into July. Foliage is 3 to 6 inches long, heavy textured, green in color and retained on the plant for more than a year. They feature flower trusses that can be 10 inches in diameter with many florets in white, lavender, pink, red and purple. Some newer hybrids have yellowish flowers.

Large leaf types are fast growing, tolerate full sun and thrive in high light-partial shade conditions where they are less susceptible to winter windburn. Roseum Elegans, catawbiense Album, Henry's Red and Scintillation are some of the familiar cultivars available at garden centers.

Small leaf types (which I call "the early rhododendrons") tend to be more delicate in appearance, but don't be deceived - these types are particularly well suited to New England weather conditions because of their superior winter performance and flower bud hardiness. Early rhododendron cultivars can start flowering in early April and most are finished by the time warmer weather comes in late May. Small trusses are 6 inches or less in diameter and come in white, lavender, pink and purple, with some of the newer cultivars showing reddish tones and doubling of petals. Leaves are 4 inches or smaller, green in summer, and resistant to winter-burn even in full sun and open, exposed conditions. They tolerate shady locations, too, but at the expense of sparser flowers and more open growth.

The unique features of the early rhododendrons qualify them as great choices for gardens in this region, and people often mistake them for azaleas. Many cultivars retain winter foliage that turns bronzy or even dark mahogany-toned during dormant seasons. This striking winter appearance creates fine opportunities for combining with colorful evergreens to enhance the appearance of the winter garden.

Many hybrids also have leaves that emit a spicy fragrance when rubbed. Examples of readily available early rhododendrons are PJM, Olga Mezitt, Landmark and Purple Gem.

The ideal time to adjust the size and shape of rhododendrons is just after they finish flowering until about mid July. Pruning and cutting back branches now allows sufficient time for the resulting new growth to fill in and set flowers for next year. For seriously overgrown plants, cut back larger branches and stems over several years to maintain a more attractive appearance. For very large specimens, exposing the thick trunks of larger plants can create an impressive effect in some landscapes, displaying mature plants in a tree-like form.

Deadheading (removing spent flowers before they set seed) is a desirable task on many of the large leaf types. In addition to improving its tidy appearance, this enables the plant to devote its energy to new growth and enhances setting flower buds for next year. Simply twisting-off the seed heads is easy, but it can be time consuming on prolific-blooming larger plants. No harm will come from leaving the seed heads - this is what happens in nature. Early rhododendrons generally do not need deadheading.

Rhododendrons are fun and easy to grow plants, and they enhance the year-round appeal for most every garden. So many sizes, colors and growth types are available to suit most every location. And once you start appreciating their features you may become addicted. The Massachusetts chapter of the American Rhododendron Society - www.arsmc.org - is a major source of information for this region. Chances are your local garden center can provide great advice, too.

R. Wayne Mezitt is the chairman of Weston Nurseries of Hopkinton and a Massachusetts certified horticulturist. He has served as president of the Massachusetts Nursery and Landscape Association, the New England Nursery Association and the American Nursery and Landscape Association, based in Washington, D.C.