''Kalmia polifolia'', previously known as ''Kalmia glauca'' and commonly called bog laurel, swamp laurel, or pale laurel, is a perennial evergreen

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

of cold acidic bogs, in the family

Ericaceae The Ericaceae () are a Family (biology), family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with about 4,250 known species spread acros ...

. It is native to north-eastern

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, from

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

Hudson Bay Hudson Bay, sometimes called Hudson's Bay (usually historically), is a large body of Saline water, saltwater in northeastern Canada with a surface area of . It is located north of Ontario, west of Quebec, northeast of Manitoba, and southeast o ...

southwards.

Etymology

The genus 'Kalmia' is named after

Pehr Kalm Pehr Kalm (6 March 1716 – 16 November 1779), also known as Peter Kalm, was a Swedish-Finnish List of explorers, explorer, botany, botanist, natural history, naturalist, and Agricultural economics, agricultural economist. He was one of the most ...

, a Swedish-Finn botanist, who was a student of

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

. The species name, 'polifolia', is

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for 'pole-leaves' or 'pole-petals'. The former species name, 'glauca', is Latin for gleaming or gray, a word ultimately derived from the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

'γλαυκός', meaning blue-green or blue-gray.

History

The plant was first described by

Friedrich Adam Julius von Wangenheim Friedrich Adam Julius von Wangenheim (8 February 1749 Sonneborn – 25 March 1800 Gumbinnen) was a German botanist specializing in forestry, and was the citing authority for a number of described eastern North American plant species. He was als ...

, a German botanist.

Distribution and habitat

''Kalmia polifolia'' is common throughout Northern North America, thriving along the Eastern American states and in

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

, as well as in every Canadian province except in

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

, although spottings have been reported of ''Kalmia polifolia'' at Rhododenron Lake, located near

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian province of British Columbia. The island is in length, in width at its widest point, and in total area, while are of land. The island is the largest ...

. Within Canada, ''Kalmia polifolia'' is very commonly found in east Nova Scotia where bog conditions are more frequent. ''Kalmia polifolia'' has also been spotted in a bog in

Surrey, England Surrey () is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Greater London to the northeast, Kent to the east, East Sussex, East and West Sussex to the south, and Hampshire and Berkshire to the wes ...

Description

''Kalmia polifolia'' flowers in April and is pollinated by bees. Bees, however, after pollinating this plant, produce a poison honey. Its seeds ripen in September. These seeds are five-parted, round, and woody. ''Kalmia polifolia'' can grow to be two feet tall. Its leaves are arranged oppositely upon its branch and grow to be an inch to an inch and a half in length and tend to be waxy with an entire and revolute margin. Below each leaf base there are ridges, where it appears as though a part of the leaf is curled around the circumference of the stem. This is especially noticeable lower on the plant. The base of the

petiole Petiole may refer to: *Petiole (botany), the stalk of a leaf, attaching the blade to the stem *Petiole (insect anatomy) In entomology, petiole is the technical term for the narrow waist of some hymenopteran insects, especially ants, bees, and ...

is pressed against the stem as its flowers cluster in a single terminal bunch, which appears to be pink or purple in colour; the near cup-shaped flower spans about three-eighths of an inch in diameter.

Uses

As medicine

''Kalmia polifolia'' can be used topically for skin wounds, disease, and inflammation, while internal uses may address bleeding and diarrhoea.

As poison

Every part of ''Kalmia polifolia'' is highly toxic and poisonous to animals and persons. Although related to ''

Kalmia angustifolia ''Kalmia angustifolia'' is a flowering shrub in the family Ericaceae, commonly known as sheep laurel. It is distributed in eastern North America from Ontario and Quebec south to Virginia. It grows commonly in dry habitats in the boreal forest, a ...

'' (lambkill), it is less toxic. Certain

indigenous Indigenous may refer to: *Indigenous peoples *Indigenous (ecology) In biogeography, a native species is indigenous to a given region or ecosystem if its presence in that region is the result of only local natural evolution (though often populari ...

groups have used the toxicity of the plant's leaves to commit suicide. According to Alaback et al., ''Kalmia polifolia'' contains a

grayanotoxin Grayanotoxins are a group of closely related neurotoxins named after ''Leucothoe grayana'', a plant native to Japan and named for 19th-century American botanist Asa Gray. Grayanotoxin I (grayanotoxane-3,5,6,10,14,16-hexol 14-acetate) is also known ...

, which when ingested lowers

blood pressure Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...

, and may cause respiratory problems, dizziness, vomiting, or

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

. According to Lewis and Elvin-Lewis, the active compounds within ''Kalmia polifolia'' include

andromedotoxin Grayanotoxins are a group of closely related neurotoxins named after ''Leucothoe grayana'', a plant native to Japan and named for 19th-century American botanist Asa Gray. Grayanotoxin I (grayanotoxane-3,5,6,10,14,16-hexol 14-acetate) is also known ...

and

arbutin β-Arbutin, also known by its International Nomenclature of Cosmetic Ingredients (INCI) name, arbutin, is a glycosylated derivative of hydroquinone. β-Arbutin is naturally present in the leaves and bark of a variety of plants, notably the bearb ...

. These compounds cause a slowing of pulse, a lowering of blood pressure, progressive paralysis and

death Death is the end of life; the irreversible cessation of all biological functions that sustain a living organism. Death eventually and inevitably occurs in all organisms. The remains of a former organism normally begin to decompose sh ...

. ''Kalmia polifolia'' has poisoned cattle, goats and sheep. For poisoning to occur, the animal must consume 0.3% of its body weight, while a dosage of 2% of an would cause severe sickness. Symptoms for affected goats include depression, nausea, salivation, vomiting, and grating of teeth. Symptoms for affected sheep include depression, staggering, nausea, recubency, salivation, and vomiting.

As food

While

caribou The reindeer or caribou (''Rangifer tarandus'') is a species of deer with circumpolar distribution, native to Arctic, subarctic, tundra, boreal, and mountainous regions of Northern Europe, Siberia, and North America. It is the only represe ...

do not have specialized food habits, they can eat most plants - preferring fungi, green leaves of deciduous shrubs, and new spring growth of sedges. They often eat ''Kalmia polifolia'' in the spring and summer; the plant comprises 11% of their dietary dry-matter protein.

For aesthetics

''Kalmia polifolia'' was planted in

Montreal Montreal is the List of towns in Quebec, largest city in the Provinces and territories of Canada, province of Quebec, the List of the largest municipalities in Canada by population, second-largest in Canada, and the List of North American cit ...

's First Nation Garden, among another 300 species planted.

Gallery

File:Kalmia polifolia 2-eheep (5097472651).jpg File:Bog laurel (Kalmia polifolia) (24276279950).jpg File:Fleurs K polifolia.JPG File:Kalmia polifolia 4 (5098087740).jpg File:The Botanical Magazine, Plate 177 (Volume 5, 1792).png, ''Kalmia polifolia'' (1792) File:45 Kalmia glauca par Pierre-Joseph Redouté.jpeg, ''Kalmia glauca'', by

Pierre-Joseph Redouté Pierre-Joseph Redouté (, 10 July 1759 – 19 June 1840), was a Painting, painter and botanist from the Austrian Netherlands, known for his watercolours of roses, lily, lilies and other flowers at the Château de Malmaison, many of which we ...

(1759–1840) File:Kalmia polifolia, by Mary Vaux Walcott.jpg, ''Kalmia polifolia'', by

Mary Vaux Walcott Mary Morris Vaux Walcott (July 31, 1860 – August 22, 1940) was an American artist and naturalist known for her watercolor paintings of wildflowers. She has been called the "Audubon of Botany." Life Vaux was born in Philadelphia, Pennsylva ...

(1860–1940)

References

External links

*
USDA Plants Profile for ''Kalmia polifolia''Jepson Manual TreatmentUC CalPhotos gallery of ''Kalmia polifolia''
{{Taxonbar, from=Q2358255 polifolia Flora of Eastern Canada Flora of the Northeastern United States Flora of the North-Central United States Flora of the Great Lakes region (North America) Flora of Saint Pierre and Miquelon Flora of the United States Flora without expected TNC conservation status