The Carlisle Mosquito Online

Friday, June 27, 2008


Swamp Azalea

Memories triggered by the smell of something are said to be more vivid than those triggered by other senses like sight or sound. They are also reputed to carry more emotional intensity. The smell of honeysuckle for me (and perhaps for George Gershwin) is enough to make me rise up singing, spread my wings and take to the sky.

The recollection is not of a particular time or place, but of a feeling that nothing can harm me. We are not yet into the fullness of summer and the honeysuckle season but in the meantime the Swamp Azalea is a good opening act.

Name. The scent of the Swamp Azalea is the reason for one of its other common names, the Swamp Honeysuckle. The scientific name is Rhododendron viscosum and along with all azaleas, rhododendrons and mountain laurels, it is a member of the heath family. The name rhododendron is from the Greek words rhodon meaning rose and dendron meaning tree. The rhodo- part of the name is more about the color rose than about a rose flower. The same root appears in words like rhodolite and rhodonite, both of which are rose-colored minerals. This particular species of Rhododendron does not (usually) have rose-colored flowers but it shares enough of the characteristics of the genus to be included.

Viscosum means sticky and it describes the flower tubes, and also explains the other common name, the Clammy Azalea.

When and where seen. Swamp Azaleas were flowering at the Cranberry Bog on June 14 and at the side of the road by the Maple Street bridge on June 21. I have seen it other years in Great Brook Farm State Park on the Tophet Trail near one of the mountain bike boardwalks. It is definitely a shrub of the swamp land but is usually on a hummock or a bank and does not have its roots directly in the water.

Description. The thing that will catch your eye first, at this time of year, is clusters of white flowers on a shrub less than eight feet tall. As you get closer you will notice the strong fragrance which some say has a touch of clove. Sometimes the flowers of the Swamp Azalea are pink or tinged with pink, but this species can always be distinguished from its relative, the Pink Azalea, by the scent, the stickiness of the flower tubes, and the later flowering season.

The Pink Azalea (which I have found in Carlisle only in the Greenough Land) flowers in May before most of its leaves are out. The Swamp Azalea blooms after the leaves are fully grown. Like other azalea flowers, the five stamens extend well beyond the petals and are very conspicuous. The petals are fused for much of their length creating a narrow tube which is covered with little hairs each equipped with a gland that exudes a sticky liquid. It is thought that the purpose of this liquid is to discourage small insects that can take nectar but are not large enough to act as pollinators. The leaves are about two inches long, dark green and glossy, and the mid-rib on the underside is hairy.

Endangered status. We should be happy to have this shrub in Carlisle and continue to protect its habitat. It is currrently not defined as vulnerable in Massachusetts but is classified by the USDA as “endangered” in Maine and “threatened” in New Hampshire.

A place in the garden. The U.S. Department of Agriculture says that the Swamp Azalea has “low palatability” for browse animals. This is an attribute that could make it a good choice for Carlisle gardens on properties with wetlands and where people would like to expand their plantings of native shrubs. It is not as showy as the hybridized Asian cultivars, but this is its homeland, and it attracts hummingbirds and butterflies. For those interested, I would try Garden in the Woods in Framingham as a possible source.

Sources: Newcombe’s Wildflower Guide, Lawrence Newcomb; Wyman’s Gardening Encyclopedia, Donald Wyman; Shrub Identification Book, George W. D. Symonds. ∆

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