Kalmia is named after the Finnish botanist Pehr Kalm, who collected it in eastern North America.
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, 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.
It has also been called spoonwood because Kalm was told by Dutch settlers of North America that Native Americans made spoons from the wood. Given its toxicity, this may be folklore rather than scientific fact.
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.