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 Kalmia subsp. var.  
Kalmia angustifolia
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Ericaceae > Kalmia var. , L.

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Kalmia is a genus of about 8 species of evergreen shrubs from 0.2-5 m tall, in the family Ericaceae. They are native to North America (mainly in the eastern half of the continent) and Cuba. They grow in acidic soils, with different species in wet acid bog habitats (K. angustifolia, K. polifolia) and dry, sandy soils (K. ericoides, K. latifolia).

Kalmia is named after the Finnish botanist Pehr Kalm, who collected it in eastern North America during the 18th Century.

The leaves are 2-12 cm long, simple lanceolate, and arranged spirally on the stems. The flowers are white, pink or purple, in corymbs of 10-50, reminiscent of Rhododendron flowers but flatter, with a star-like calyx of five conjoined petals; each flower is 1-3 cm diameter. The fruit is a five-lobed capsule, which splits to release the numerous small seeds.

The foliage is toxic if eaten, with sheep being particularly prone to poisoning, hence the name lambkill used for some of the species. Other names for Kalmia, particularly Kalmia angustifolia, are sheep-laurel, lamb-kill, calf-kill, kill-kid, and sheep-poison,[1] which may be written with or without the hyphen. (See species list below.) "Kid" here refers to a young goat, not a human child, but the foliage and twigs are toxic to humans as well.

Kalmias are popular garden shrubs, grown for their decorative flowers. They should not be planted where they are accessible to livestock due to the toxicity.

Standard Cyclopedia of Horticulture

Kalmia (after Peter Kalm, Swedish botanist, traveled from 1748 to 1751 in North America). Ericaceae. American Laurel. Ornamental shrubs grown for their handsome flowers and foliage.

Evergreen, rarely deciduous: lvs. alternate or opposite, short-petioled, entire: fls. in terminal or lateral corymbs or umbels, rarely solitary; calyx 5-parted; corolla saucer-shaped or broadly campanulate, 5-lobed: stamens 10, with slender filaments, the anthers held back in little pouches of the corolla, springing up suddenly and discharging the pollen if touched; ovary 5-celled, superior: caps, globular, parting into 5 valves, with numerous minute seeds.—Seven species in E. N. Amer. and Cuba. The lvs. of the kalmias are said to be poisonous to animals, especially those of K. angustifolia. The fl. of Kalmia is one of those proposed as a national floral emblem, especially on account of the exquisite symmetrical beauty of the single blossom. Kalmia is a purely American genus, but unfortunately it is popularly known only in the eastern states.

The kalmias are medium-sized or low shrubs, very rarely small trees with purple, pink or nearly white, cup-shaped flowers in showy terminal corymbs or in axillary umbels, rarely solitary, followed by small capsular fruits. Kalmia angustifolia and K. polifolia are hardy North, and also the most ornamental member of the genus, K. latifolia, which next to rhododendron is the most beautiful flowering hardy evergreen. Massed in groups or as single specimen on the lawn, it is one of the most decorative plants when covered with its abundant pink flowers. Even small plants produce flowers. The foliage is very decorative, contrasting well with the red and yellowish branches. The species is easily forced and makes a very handsome pot-plant. The other species are pretty border plants for evergreen shrubberies.

The kalmias thrive well in a sandy, peaty or loamy soil, but dislike clay and limestone. They grow almost as well in swamps as in drier locations and prefer partly shaded situations, but thrive well also in sunny places, provided there be sufficient moisture. They require generally almost the same treatment as the hardy rhododendron, but are less particular about soil and position. Transplanting, if carefully done either early in fall or in spring, is not difficult; a mulching the first season after planting will be of much advantage to keep the roots from drying in summer and from frost in winter. Propagation is usually by seeds sown in sandy, peaty soil in pans or boxes in early spring and kept in a coldframe or greenhouse. The seedlings should be pricked off as soon as they can be handled, and after they are again established gradually hardened off and the following year transplanted in frames or beds outdoors. Varieties of K. latifolia are usually increased by side-grafting on seedlings in the greenhouse or by layers, since it grows less readily from cuttings, while the other species may be propagated by cuttings of half-ripened wood under glass.

The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.



Pests and diseases


The related Kalmiopsis (Kalmiopsis leachiana) is a rare shrub native to the Siskiyou Mountains of southwest Oregon.



  1. Natural History Education, Science, Technology regarding alternate names, accessed March 30, 2007.

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