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Species In Our Midst
Rhododendron groenlandicum

by Bill Sweeney

Rhododendron groenlandicum
Picture by S & J Perkins
Rhododendron groenlandicum in Salem, NH

Rhododendron groenlandicum

Suddenly, we have a new rhododendron in New England! Well, actually it's not new, it's just been reclassified. As of 1990, botanists K. A. Kron and W. S. Judd (Edinburgh Journal of Botany, 47/2,1990) have decreed that the Genus Ledum should be lumped with the Genus Rhododendron. They now place it in the new Subsection Ledum, in Section Rhododendron, Subgenus Rhododendron with other scaly leafed (lepidote) rhododendrons.

Rhododendron groenlandicum grows in cold, boggy soil, typically amidst rocky scree, such as at the heights of the White Mountains. Extensive patches of it can be seen in the Alpine Garden near the summit of Mount Washington. It has been found as far south as northern New Jersey and Pennsylvania, in Ohio and Michigan, and as far west as Alberta Province and Washington State. A related species, Rhododendron neoglandulosum, is found in the Pacific Northwest. A few similar species and subspecies are found in northern Europe, Siberia, and northern Japan. Of all these related species, Rhododendron groenlandicum, is the most common in gardens, particularly in cool, damp climates such as Scotland.

In the White Mountains, Rhododendron groenlandicum rarely grows over one foot tall, though it can grow to three or even six feet in areas with gentler winds and weather. Young shoots are scaly and are covered with reddish hairy felt (tomentum) on top and sometimes with glands. The leaves are small (1/2 to 2 inches) bright evergreen, thick and leathery, growing on alternate sides of the stems; they are elliptic or narrowly oblong, and are more pointed at the tip. The undersides are covered with a thick, wooly, rust-colored indumentum. The leaves are strongly rolled at the edges and are highly aromatic, which led to the common name for the plant: Labrador Tea. The leaves were used to brew "tea" by the early settlers. Rhododendron neoglandulosum, the Trapper's Tea of the Northwest, has broader, flatter leaves, and lacks indumentum.

The tiny white flowers, not over 3/8-inch wide, have five white petals and seven to twelve conspicuous stamens. They form tight clusters of up to 30 individual flowers. To my eye, a plant in bloom seems to have fuzzy balls of cotton at the ends of its branches.

Strangely, and perhaps uniquely for a rhododendron, the seed capsule opens from the bottom up. Some people still don't believe that the plant is truly a rhododendron because of this characteristic (Greer). The capsules tend to hang downwards when ripe, thus the "top" is now below the "bottom", so possibly the upside-down opening is a compensation that the plant has developed to correct for the upside-down hang of the capsule.

Bill Sweeney, Concord, MA

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