Shrubs of the Adirondacks:
Bog Laurel (Kalmia polifolia)

Shrubs of the Adironack Park: Bog Laurel on Barnum Bog (31 May 2014).
Shrubs of the Adirondacks: Bog Laurel has leathery leaves with smooth edges which turn inward. The underside of the leaves are whitish. Bog Laurel on Barnum Bog  (31 May 2014).

Bog Laurel (Kalmia polifolia) is an evergreen shrub which flowers in mid-to late-spring and grows in bogs in the Adirondack Mountains of upstate New York.

Bog Laurel is a member of the Heath family. It is also called Pale Laurel, Swamp Laurel, and Bog Kalmia. The scientific name is a reference to Peter Kalm, a Swedish botanist who lived in the 18th century and was a student of Linnaeus. Linnaeus reportedly named the genus in a tribute to his student, who was one of the first scientists to examine and study the flora of eastern North America.


Identification of Bog Laurel

Shrubs of the Adirondack Park: Bog Laurel on the margins of Heron Marsh (19 May 2012).
Shrubs of the Adirondacks: Bog Laurel's brilliant pink flowers are one-third to one-half inch wide and usually appear in late May to early June in most parts of the Adirondacks. Bog Laurel on the margins of Heron Marsh (19 May 2012).

Bog Laurel is a small evergreen shrub, six to 22 inches tall. The branches and twigs are two edged. The bark is brown to black.

The leaves are opposite, meaning that two leaves are attached at the same location (a node) on a stem, but opposite one another, on either side of the stem. Bog Laurel's leaves are relatively small (1-1.5 inches long), lance-shaped and leathery, with smooth edges that turn downward. The leaf blade has one main vein running from the base toward the tip. The underside of the leaves has whitish hairs.

There are several competing theories as to why Bog Laurel and certain other members of the Heath Family have adopted these features. One theory suggests that these features reflect a strategy for reducing water loss. Although the bog is frozen in winter, the plant's evergreen leaves are still exposed to the wind, except during periods of deep snow. The small leaf size, the thickness of the leaf, and the rolled-under margins all help minimize water loss. A competing school of thought contends that these features represent an adaptation to nutrient deficiency, not potential water loss. A third theory is that the lower growth forms and tough, leathery leaves of plants like Bog Laurel and Labrador Tea are mainly adaptations to snow and cold. In any event, the leathery, in-rolled leaves provide convenient clues to Bog Laurel's identity.

In spring, the Bog Laurel produces clusters of up to thirteen small, cup-shaped pink flowers. The flowers are 1/3 to 1/2 inch in diameter and are saucer shaped, with five sides. There are ten white stamens, with dark tips, surrounding a pink style in the center. The flowers are pollinated by bees. This plant usually flowers from late May to about mid-June in the Adirondacks. Flowering times for Bog Laurels growing on mountain summits in the High Peaks is a week or so later.

Bog Laurel fruit is a cluster of long-stemmed dry, woody capsules. Each five-chambered round capsule is about a quarter of an inch in diameter, with the remains of the pistil at the top. In the Adirondacks, the fruit generally appears in August.

Shrubs of the Adirondack Park: Bog Laurel on Barnum Bog (30 May 2015).
Shrubs of the Adirondacks: Bog Laurel can be distinguished from Sheep Laurel by the placement of the flowers. Bog Laurel flowers grow in clusters at the end of the stem, while the flowers of Sheep Laurel grow on last year's growth. Bog Laurel on Barnum Bog (30 May 2015).

Keys to identifying the Bog Laurel and differentiating it from other leathery-leafed plants growing in swampy or boggy habitats include leaf arrangement, shape, and color, as well as the color and arrangement of the flowers.

  • Several features differentiate Bog Laurel from Bog Rosemary. Although both species feature in-rolled leaves, Bog Laurel's opposite leaves contrast with Bog Rosemary's alternate leaves. Also, Bog Rosemary's bell-shaped flowers are very different from the cup-shaped flowers of Bog Laurel. Finally, Bog Rosemary leaves have a blue-gray cast, while Bog Laurel leaves are shiny green.
  • Bog Laurel can be distinguished from Sheep Laurel by the placement of its flowers. While the flowers are quite similar, those of the Bog Laurel form clusters at the end of the stem. The flowers of the Sheep Laurel, by contrast, appear a few inches from the top of the stem, with newer leaves above the cluster of flowers. In addition, Sheep Laurel leaves lack the in-rolled edges and white undersides of Bog Laurel leaves. Moreover, Sheep Laurel twigs do not feature two edges.
  • Bog Laurel can be distinguished from Leatherleaf, since the latter has alternate leaves. In addition, the leaves of the Leatherleaf are not in-rolled and the undersides have small brown scales. The flowers are also quite different. The white Leatherleaf bells appear on axils of the current year's leaves, forming a one-side raceme, while the pink Bog Laurel flowers appear in clusters at the end of the branch.
  • Although the leaves of Labrador Tea also turn downward (like those of Bog Laurel), they are arranged alternately, contrasting with Bog Laurel's opposite leaves. The underside of Labrador Tea leaves are covered with a dense mat of tangled woolly hairs which are white on young leaves and rusty on mature leaves. Finally, the flowers are very different. Labrador Tea has rounded clusters of white flowers, contrasting with Bog Laurel's cup-shaped pink flowers.

Uses of Bog Laurel

Bog Laurel is highly toxic and should not be ingested. Its poisonous foliage and nectar contains toxic resins called grayanotoxins. It may be fatal if eaten.

Given these dangers, this species is rarely, if at all, used in modern herbalism. At one time, some native American groups are said to have used the leaves of the plant as an external treatment for skin ailments. For instance, the Kwakiuti reportedly used a decoction of leaves as a wash for open sores and wounds that would not heal. The Tlingit used an infusion of the whole plant for unspecified skin ailments.

Wildlife Value of Bog Laurel

Bog Laurel has limited importance to wildlife. The food value of this species is limited, since the fruit is dry and minute, and the foliage contains chemicals that are toxic to at least some animals. However, the bog communities where Bog Laurel flourishes are extremely important to some bird species, including the Palm Warbler and Lincoln's Sparrow.

Distribution of Bog Laurel

Bog Laurel is found mainly in the northeastern United States and Canada. Its range includes Labrador to Alaska, south to New Jersey, Pennsylvania, the Great Lakes, and Montana.

Bog Laurel occurs in most New York State counties in the eastern part of the state. It has been reported in all of the counties within in the Adirondack Park Blue Line, with the exception of Saratoga County.

Habitat of Bog Laurel

Bog Laurel can grow in part shade, shade, or sun. In the Adirondacks, you can find this species either in wetlands on lower elevations or on mountain summits in the High Peaks. Bog Laurel is found in several ecological communities in the Adirondack Park, including:

One of the most convenient places to study Bog Laurel is on Barnum Bog, an acidic bog that can be accessed along the Boreal Life Trail boardwalk.

You can also find Bog Laurel growing on the summits of Adirondack mountains in the High Peaks region, including Marcy, Algonquin, Wright, Iroquois, Coldin, Haystack, Basin, Saddleback, Gothics, Dix, and Whiteface.


References

Michael Kudish. Adirondack Upland Flora: An Ecological Perspective (Saranac, New York: The Chauncy Press, 1992), pp. 141-142.

New York Flora Association.  New York Flora Atlas. Bog-rosemary. Andromeda polifolia L. var. latifolia Aiton. Retrieved 14 March 2017.

United States Department of Agriculture. The Plants Database. Andromeda polifolia L. Bog Rosemary. Retrieved 14 March 2017.

United States Department of Agriculture. Fire Effects Information System (FEIS).  Species Reviews. Andromeda polifolia.  Retrieved 14 March 2017.

Flora of NorthAmerica. Andromeda polifolia Linnaeus var. latifolia Aiton. Retrieved 14 March 2017.  

Lady Bird Johnson Wildflower Center. Native Plant Database. Retrieved 14 March 2017.

Northern Forest Atlas. Images.  Bog Rosemary.  Retrieved 14 March 2017.

New York State. Adirondack Park Agency. Preliminary List of Species Native Within the Adirondack Park Listed Alphabetically by Scientific Name and Sorted by Habit. Volume 1. Updated 10.23.2006, p. 9. Retrieved 26 January 2017.

New York Natural Heritage Program. 2015.  Online Conservation Guide for Dwarf Shrub Bog. Retrieved 22 February 2017.

New York Natural Heritage Program. 2015.  Online Conservation Guide for Inland Poor Fen. Retrieved 22 February 2017.

New York Natural Heritage Program. 2015. Online Conservation Guide for Medium Fen. Retrieved 14 March 2017.

New York Natural Heritage Program. 2015.  Online Conservation Guide for Patterned Peatland. Retrieved 22 February 2017.

University of Michigan. Native American Ethnobotany. A Database of Foods, Drugs, Dyes and Fibers of Native American Peoples, Derived from Plants. Andromeda polifolia L. Bog Rosemary.  Retrieved 14 March 2017.

NatureServe Explorer. Online Encyclopedia of Life. Retrieved 29 March 2015.

Plants for a Future. Database. Retrieved 29 March 2015.

University of Wisconsin. Flora of Wisconsin. Retrieved 29 March 2015.

University of Wisconsin. Shrubs of Wisconsin. Retrieved 29 March 2015.

Connecticut Wildflowers. Wildflower Guide. Retrieved 29 March 2015.

John Eastman. The Book of Swamp and Bog: Trees, Shrubs, and Wildflowers of Eastern Freshwater Wetlands (Stackpole Books, 1995), pp. 25-27.

The Cornell Lab of Ornithology. Birds of North America.  Yellow-bellied Flycatcher.  Subscription web site. Retrieved 14 March 2017.

Allen J. Combes. Dictionary of Plant Names (Timber Press, 1994), p. 11.

ENature. Wildflower Field Guide. Retrieved 29 March 2015.

Minnesota Wildflowers. Database. Retrieved 29 March 2015.

New England Wildflower Society. Andromeda polifolia. Retrieved 29 March 2015.

Birds of the Boreal Life Trail. Barnum Bog Birds. VIC Birding Trail Guide (June 2015).

Doug Ladd. North Woods Wildflowers (Falcon Publishing, 2001), p. 76.

Lawrence Newcomb. Newcomb's Wildflower Guide (Little Brown and Company, 1977), pp. 292-293.

Meiyin Wu and Dennis Kalma. Wetland Plants of the Adirondacks. Ferns, Woody Plants, and Graminoids (Trafford Publishing, 2010), pp. 39, 61, 62.

Charles W. Johnson. Bogs of the Northeast (University Press of New England, 1985), p. 29.

Donald D. Cox.  A Naturalist's Guide to Wetland Plants.  An Ecology for Eastern North America (Syracuse University Press, 2002), pp. 83-84, 90.

John Eastman. The Book of Swamp and Bog. Trees, Shrubs, and Wildflowers of Eastern Freshwater Wetlands (Stackpole Books, 1995), pp. 25-26.

David M. Brandenburg. Field Guide to Wildflowers of North America (Sterling Publishing Company, Inc., 2010), p. 215.

George A. Petrides. A Field Guide to Trees and Shrubs (Houghton Mifflin Company, 1958, 1972), pp. 288, 364-365.

Janet Lyons and Sandra Jordon. Walking the Wetlands. A Hiker's Guide to Common Plants and Animals of Marshes, Bogs, and Swamps (John Wiley & Sons, Inc., 1989), pp. 91-92.

Shrubs of the Adirondack Park



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