Kalmia latifolia
Native to eastern North America, mountain laurel (Kalmia latifolia) is one of the most beautiful native flowering shrubs. This large broadleaf evergreen blooms in late spring. Its bright pale pink flowers open from deeper pink buds. The blooms are bell-shaped, white to pink with deep rose spots inside. Brown fruits follow that persist into winter. Its year-round foliage, leathery and glossy, changes from light green to dark green to purple throughout the year.
But mountain laurel has more going for it than ‘just beautiful’. Although it flourishes in part shade with moist, acidic well-drained soil, mountain laurel tolerates full sun to full shade too and adapts to a range of soils from sandy to shallow, rocky soil. It can even grow in dry sites. And it is deer and rabbit resistant.
Mountain laurel has an unusual method of dispensing its pollen. As the flower grows, the filament of its stamens are bent and brought into tension. When an insect lands on the flower, the tension is released, catapulting the pollen forcefully onto the insect. Experiments have shown the flower is able to fling its pollen up to 15 cm/6 in.
Then there is the highly poisonous side of mountain laurel. Every part of Kalmia latifolia is extremely toxic and dangerous to humans, pets, and livestock. The bark, the leaves, the flowers, and the seeds contain toxins that can disrupt muscle, nerve and heart function. In severe cases, ingestion can lead to coma and death within days. Children have been poisoned by just sucking on the flower. Even honey made from mountain laurel pollen is toxic. Grayanotoxin and arbutin are the two deadly poisons in mountain laurel. Grayanotoxins are a group of closely related neurotoxins produced by some plants in the Heather Family.
Being highly toxic works in favour for mountain laurel though. When the American chestnut (Castanea dentata) forests died out in eastern North America, mountain laurel began spreading, enjoying the new conditions of more light. It never had to worry about deer munching it down to nothing.
Story by Hughie Jones and all photos except for the light pink flowers. The photo with the dark pink flowers is of its cultivar ‘Pink Charm’ blooming in summer.