Kalmia Latifolia | Ericaceae

Submission: Natalia Jacobs and Katie Watt

Identification:

Leaves: alternate, simple, evergreen, elliptical, leathery, and have entire margins;¾ to 4 inches long, and 1 to 2 inches wide. 

Twigs: long, narrow, and glabrous; furrows and ridges are also present.

Bark: thin, flaky, and dark reddish brown in color.

Buds: range from pink to deep red in color depending on the cultivar;form corymb inflorescence; flower buds are formed in prior growing season; vegetative buds consist of two scales. 

Flowers: range from white, pink, and red and are in a distinctive, geometric looking shape that resembles an origami bowl;en stamens with red tips are suppressed against the creases of the flower; the base of the stamens are surrounded by a circle of red markings. 

Fruit: globose, woody capsule. 

Silvics: 

Mountain laurel is native to eastern North America and typically found in a variety of forest types, including spruce-fir, northern hardwood, mixed hardwood, pine-hardwood, oak-hickory, and eastern white pine forests. It can also be found growing among the understories of longleaf pine forests and on savanas. Mountain laurel can tolerate a variety of light conditions from full sun to full shade, which allows it to tolerate shaded regions of the understory, forest openings/clearings, and forest edge habitat. However, Mountain laurel seedlings typically grow best in partial shade. Mountain laurel also grows well in sand deposits, ravines, balds, and dry upper slopes of mountains. While a mature Mountain laurel is typically 6.5 to 10 feet tall, specimens have been measured at nearly 40 ft tall in the Appalachian mountain range.

Mountain laurel thrives in habitats with acidic soil (pH <6) that is moist, well drained, nutrient rich, high in organic matter, and a bit sandy. Mountain laurel is drought resistant, so it can tolerate varying levels of precipitation.

Natural History: 

When one names the characteristics of a shrub, “physical speed” will most likely not be on the list. It may be surprising to hear then that the Harvard Gazette has called Mountain Laurel “one of the fastest-moving plants on the globe.” This is due to the plant’s very unique way of dispersing pollen. The flowers have a brilliant design where the stamens hold a great amount of tension. When a pollinator lands, their weight sets off a reaction in which the stamen catapults up, releasing pollen onto the pollinator. Mountain laurel can also spreads especially fast after forest fires as a result of asexual reproduction through basal burls and the speed of spread increases as the severity of fire increases.

Several characteristics of Mountain laurel have led to the formation of a few nicknames for the plant. Areas where the plant grows in dense patches are fondly referred to by some people as “Laurel Hells.” Another of its colloquial names, “Spoonwood,” reflects its versatility and use for utensil making by Indigenous peoples. Mountain laurel wood is strong and heavy, which lends it to many uses. Indigenous people and Europeans have used Mountain laurel wood to construct furniture, bowls, and wreaths.  

Though still very popular amongst florists today for arrangements and wreaths, the harvesting of Mountain Laurel peaked during the 1920s at an estimated twenty million pounds per year. As a result of its popularity, Mountain Laurel was named the state flower of Pennsylvania in 1933. While all parts of Mountain laurel are poisonous and can be lethal in large doses to humans and many species of livestock, other animals, such as white-tailed deer, eastern cottontails, black bear, and ruffed grouse, often rely on Mountain laurel in times of near starvation. Even though Mountain laurel can be quite toxic, there is some evidence of its usage as a painkiller by people of the Cherokee Nation.  

Sources:

League, K. R. 2005. Kalmia latifolia. In: Fire Effects Information System. [accessed 2023 November 24]. https://www.fs.usda.gov/database/feis/plants/shrub/kallat/all.html 

Shane J. 2008. Dendrology Handbook, University of Vermont, Unpublished. p. 75.

“Mountain Laurel.” Penn State Extension, extension.psu.edu/mountain-laurel. [Accessed 30 Nov. 2023]. 

Hamel, Paul B. and Mary U. Chiltoskey 1975 Cherokee Plants and Their Uses – A 400 Year History. Sylva, N.C. Herald Publishing Co. p. 42.