Sheep Laurel
- katemacquarrie22
- Jul 13
- 2 min read
This time of year, beautiful wildflowers are blooming in all of PEI’s habitats. Many people miss out on seeing those that thrive in bogs, such as the lovely Sheep Laurel (Kalmia angustifolia).
Bogs are unforgiving places for plants. The ‘soil’ (peat) is water-logged, acidic, low in oxygen, and nutrient poor. Species that live in bogs sometimes develop useful adaptations that give them a leg up, and Sheep Laurel has several.
Plants and fungi often form mutually-beneficial relationships: the fungi share nutrients with the plants, while the plants provide the fungi with sugar they make via photosynthesis. This can be especially important for plants living in inhospitable environments such as bogs, and Sheep Laurel takes full advantage of this. It’s been shown that the more water-logged (and thus more anoxic) the bog environment is, the greater the presence of mycorrhizal fungi in Sheep Laurel roots.
It's nice if you can beat the competition but even better if you can reduce it. Sheep Laurel has the ability to suppress root and shoot growth of nearby conifer trees, especially Black Spruce (Picea mariana, the most common tree in our bogs). The exact mechanism is unknown, but Sheep Laurel has been shown to directly reduce the trees’ ability to use nitrogen and phosphorus. It’s been suggested that Sheep Laurel releases substances into the peat which interfere with the mycorrhizal fungi of Black Spruce – a sort of botanical chemical warfare known as allelopathy.
Those beautiful flowers support an adaptation, too. If you look closely, you’ll notice each one has a central pillar (the female pistil) surrounded by 10 little filaments bent back into pockets in the petals, under tension like tiny catapults. Those are the anthers – male, pollen-bearing structures.
When a pollinator lands on the flower, it triggers the catapult and releases the anther. This propels the pollen onto the pollinator; you can see the process yourself by gently pulling back a petal to release an anther. In this way, Sheep Laurel hedges its bets and covers the insect in pollen rather than waiting for it to pick some up by chance. This also helps with self-fertilization if pollinators are scarce: raindrops, wind, and other forces can cause the catapults to pop, tossing pollen onto the pistil.
While there are edible plants in bogs, Sheep Laurel is not one. All parts of this plant are toxic and contain grayanotoxins, a group of chemicals that can cause dizziness, confusion, low blood pressure, slow heartbeat, vomiting, abdominal pain, and – in severe cases – coma and death.
While I haven’t come across any records of human fatalities attributed to Sheep Laurel, there have been hospitalizations due to consumption of related grayanotoxin-containing species (especially Rhododendron), as well as honey made from those plants (aka ‘mad honey’). Sheep Laurel is frequently fatal to cattle, goats, and sheep in areas where pastures are near bogs or wet woodland and is the most common cause of livestock poisoning in Newfoundland and Labrador. Appropriately, Lambkill is another common name for this plant.
Despite its toxicity, Sheep Laurel is a beautiful, native, and well-adapted part of PEI Untamed!
