The Carlisle Mosquito Online

Friday, June 26, 2009


Mountain Laurel

Mountain Laurel is not common in the wild in Carlisle. I have found it only in one place in the Greenough woods. It is growing near a stream and was still in bloom last weekend (June 21).

Name: Mountain Laurel is Kalmia latifolia. It can cover much of a mountainside (as in parts of Connecticut and in the Appalachians) and while it is native to eastern North America the genus is named for Peter Kalm of Sweden. He was a student of Carolus Linnaeus and came to the Americas in 1748 to find plants that would grow in Sweden and satisfy some commercial need as food, animal fodder, dye, etc. He stayed three years and explored Pennsylvania, New Jersey, New York, and parts of southern Canada. He documented flora and fauna and also the colonial lifestyle. He eventually gave his collection of laurels and other plants to Linnaeus. The species name, latifolia, is from the Latin ‘latus’ meaning broad and ‘folius’ meaning leaf, making this the ‘broad-leaved’ laurel. Other common names for Mountain Laurel are Calico-bush, Ivy Bush, and spoonwood.

Family: Mountain Laurel is a member of the heath family which in addition to the heaths, includes Rhododendrons, Azaleas, blueberries, and cranberries – and of course the other species of Kalmia.

Description: Mountain Laurel is a many-stemmed evergreen shrub that can reach about 20 feet in height. The flowers grow in clusters at the tip of the branches. The buds are pink and knobby and open to white flowers with pink or purple lines. Most of us know the plant from the nursery trade where many cultivars are available with a huge variety of patterns of pink and white in the flowers.

Fungal friends: The Mountain Laurel has symbiotic relationships with soil-dwelling mycorrhizal fungi. Some of these are on the roots (ectomycorrhizal) and some are within the roots (endomycorrhizal). Both kinds take food from the laurel and ‘pay’ for it by improving the laurel’s ability to absorb water and nutrients and thereby making it more healthy. They may even help further by combating other fungi that would be harmful to the laurel.

Pollination: Both the leaves and flowers are poisonous and the nectar is supposedly capable of poisoning honey, but another source said that honey bees rarely visit the plant and the primary pollinator is the bumblebee. The pollination mechanism is a distinguishing feature of Kalmias. The knobs on the flower buds are pouches for the stamen tips which are driven into the pouches as the flower opens causing the stamens to bend backward and a lot of tension to build up. The bumbling bumblebee is heavy enough to trip the the spring, get a coating of pollen, and carry it to the next flower. The flower stalks have sticky hairs which keep down the visits by smaller insects who would be ineffective pollinators.

Uses: Appalachian mountain people used to make a yellow dye from the leaves and early colonists used the wood to make tool handles, weaving shuttles, and pipes. Native Americans made small dishes and spoons from the wood, hence the name ‘spoonwood’. In the wild where it is a common understory shrub, it serves to prevent soil erosion and water run-off. Mountain Laurel is widely used as a decorative garden shrub. The toxicity of the leaves is enough to deter livestock and I found it on several different lists of deer-resistant plants. The ones in Greenough have certainly survived the years.

Sources: Kalmia, Mountain Laurel and Related Species, Richard Jaynes; Audubon Field Guide to North American Trees, Eastern Region, Elbert L. Little; Shrub Identification Book, George W. D. Symonds.

© 2009 The Carlisle Mosquito