Wednesday, March 2, 2016

Mountain Laurel

A Mountain Laurel shrub in bloom.

     The evergreen shrub Kalmia latifolia goes by a variety of names: Mountain Laurel, Calico Bush, Spoonwood, Ivybush, Calmoun, Mountain Ivy, and American Laurel. Its Genus is named after Peter Kalm, a Swedish botanist and friend of Linnaeus who named it after him. Kalm introduced it into Europe, thinking it the most beautiful tree he had seen during his travels. Indeed, when it is in bloom with its white to pink flowers in May or June, it can be be a glorious sight. No wonder it is the state flower of both Connecticut and Pennsylvania. 

The spring-loaded flowers of Calico Bush.

     The blooms have an interesting way of dispersing pollen onto visiting insects, mostly bumblebees. Each flower has 10 spring-like stamens that are lodged in pockets on the fused petals that form the flower itself. When a pollinator lands, it triggers the stamens into launching pollen in a catapult-like fashion onto the back of of the insect. The pollen can be hurled up to a foot away, sometimes landing on other Mountain Laurel flowers and pollinating them as well. The resulting seed pods contain 600 or so seeds, which germinate best on moss.

Mountain Laurel seed pods.

     Mountain Laurel tends to grow on dry hillsides, in wooded areas, rarely reaching 30' at most. This member of the Heath (Ericaceae) family can form dense thickets of crooked trunks since it can root or layer where its branches touch the ground. These stands provide good cover and nesting sites for many animals. 
     While the leaves are toxic, protecting it from deer browse in normal conditions, 33 caterpillar species have been recorded feeding on it. Even the flowers are poisonous, producing bitter honey for any bees visiting them, though apparently with no ill effects to the bees themselves. Peculiar to this plant are blotches on the leaves, produced by Mycosphaerella colorata fungi. 

Mountain Laurel Leaf Spot fungus is usually found on the leaves.

     In winter, the under sides of the leaves sometimes have white-edged spots. These are the eggs of Coccidae scale insect eggs, a favorite food of chickadees and kinglets. The eggs are actually covered over by the shells that were their parents.
     Despite the toxicity, Mountain Laurel has been used by people for a variety of purposes. According to ethnobotanist Daniel Moerman, various Native American Indian tribes made use of it. The Cherokee used a leaf infusion on cuts and scratches. A concoction was rubbed over the skin to treat rheumatism. As a liniment, it was believed to be a good treatment for cramps. It was even used as an insecticidal soap. It was even rumored to be used a suicidal drink. The Cree also considered it poisonous, yet still sometimes used it for diarrhea. 
     Confederate doctor Francis Porcher, tasked with coming up with alternative medicines due to shortages caused by Union blockades during the Civil War, thought it could be used to treat syphilis, heart disease, and skin afflictions. The hard wood has been used to make spoons, thus its name of Spoonwood, but burls from its trunk were also used to fashion tobacco pipes.
     This is an interesting shrub, as if its beautiful floral displays in dark woods were no enough of a reason to like this plant.

I find even the flower buds of Mountain Laurel beautiful.


  1. I've heard that mountain laurel is notoriously hard to propagate and that seeds won't generate unless they fall on moss. What do you think of the smaller, more dense cultivars sold by nurseries?