Scientific name: Kalmia latifolia
The plant is naturally found on rocky slopes and mountainous forest areas. It thrives in acidic soil, preferring a soil pH in the 4.5 to 5.5 range. The plant often grows in large thickets, covering great areas of forest floor. In the Appalachians, it can become tree-sized but is a shrub farther north. The species is a frequent component of oak-heath forests.
Year-round evergreen leaves. Elliptic, alternate, leathery, glossy evergreen leaves (to 5″ long) are dark green above and yellow green beneath and reminiscent to the leaves of rhododendrons.
Blooming May – June, this shrub produces flowers that vary in color from white to pink-rose to deep rose – all with unique purple markings – which measure up to 1 inch in diameter. They occur in flat-top clusters.
Kalmia latifolia is notable for its unusual method of dispensing its pollen. As the flower grows, the filaments of its stamens are bent and brought into tension. When an insect lands on the flower, the tension is released, catapulting the pollen forcefully onto the insect. Experiments have shown the flower capable of flinging its pollen up to 6 inches.
Mountain laurel has done exceedingly well over the last century, says the Forest Service. Three factors, among others, account for much of that.
The loss of the American chestnut tree to blight opened the forest canopy, as did oak deforestation caused by gypsy moths. Add to that fire suppression – a hallmark of forest management that’s slowly going away – and quick-growing mountain laurel spread across the landscape.
Did You Know?
Although it is a member of the blueberry family, no part of the plant is safe to eat. Even the pollen is poisonous which means that honey made from its pollen is also toxic. Besides being potentially lethal to humans, it is also poisonous to deer, cattle, horses and goats.
More on Trees and Shrubs in Lewisboro
Lewisboro was once entirely forested except for patches of open field caused by fire and wetlands and ponds which were expanded by beaver dams. Although it is hard to believe, by 1800 most of Lewisboro’s forests had been cut down and replaced by farms. In 1820 so many trees had been cleared that there was no shade anywhere along the route from Boston to New York. But by the mid-1800’s farming here became uneconomical and as farms were abandoned, the forests began to re-grow. Today, 70% of New York is once again forest, what some call ‘the great environmental story of the United States’. These new forests provide us with beauty and recreation, clean air and water, flood control, erosion prevention, carbon sequestration, cooler temperatures and habitat for other plants, insects, birds and other wildlife.
 An Explosion of Green. B. Mckibben. Atlantic Monthly 275 (April 1995): 61-83.