It is a killer.
Not a lady killer, but a livestock killer. The common names of Kalma angustifolia say it all; sheepkill, lambkill and calfkill. With aliases like that, you’d think that this plant definitely has a public relations problem on its hands.
Its common names speak to a characteristic that is worrisome (to say the least) for the shepherd. This plant is a mean, green poisoning machine!
Keepers of livestock, be warned — sheep laurel (its most common name) is deadly to your animals. During the winter and early spring, when green plants are in short supply, domestic animals are drawn (hazardously) to this woodland evergreen species.
It only takes a little bit of leaves to be deadly; consider that if a sheep eats only 0.15 per cent of its body weight in this foliage, it can result in toxic symptoms that can cause death. For cattle, the magic number is 0.20 per cent and for goats, 0.25 per cent, so it doesn’t take much more than a taste. Less than a quarter of one per cent of your body weight isn’t a lot to eat.
Its bigger sister species, mountain laurel (Kalma latifolia), can cause even bigger problems. In the 18th century, Professor Smith Barton of Philadelphia noted its deadly properties when he observed that the “Indians make use of a decoction of the leaves to destroy themselves.”
Perhaps the two Island species of laurel should contain warning labels, or maybe we need to sign a waiver before taking a walk in the woods. While this may seem like an overreaction, the toxic qualities of laurel might just justify these cautions. Although I am unsure of the human reaction to these plants, it is always better to be safe than sorry.
Sheep laurel is plentiful in Island woodlands. It is an understory plant that reaches a few feet in height. It becomes apparent two times per year. One is during the early summer when it has clusters of pink flowers growing from the middle of its stem. The other time is now and through the winter, when this evergreen is one of the few plants that retains its green (though droopy) leaves through the season. Also notable is the dry brown fruit capsules apparent throughout the winter.
Its sister species, mountain laurel, is much less common on Island. It seems reasonable, since we are not known as a mountainous region with our lofty summits of all of 312-ish feet. There are only a few sites to see this larger shrub, which may have been planted by human hands. One of these locations is along an ancient way that runs near Pennywise Path.
On a walk, it would be easy to miss this small grove of mountain laurel plants, since these shrubs resemble high bush blueberry. They both have crooked stems and rough, peely bark, but then you notice that it has leaves present during the winter. The ‘aha’ moment follows, and it is becomes clear that indeed it is not deciduous blueberry, but rather evergreen mountain laurel.
The wood of the mountain laurel has some qualities that perhaps compensate for its otherwise deadly nature. Linnaeus’s student, Peter Kalm, for whom the genus Kalma is named, noted that “the spoon tree (mountain laurel), which never grows to a great height, was seen in several places. The Swedes here have named it thus, because the Indians used to make their spoons and trowels of its wood.” Manasseh Cutler, a representative from Massachusetts who was involved in the whaling trade in Edgartown and became a noted botanist and astronomer, concurred when he praised what he called Great Laurel: “They are large, of a soft texture, and easily wrought when green; but when thoroughly dry, become very hard and smooth.”
So even with its deadly sin, these Kalmas do have some good karma as well. While lethal for livestock to eat, they are useful to eat with (as the name spoon tree suggests). I can only say that even though some good mixes with the bad, these particular plants cannot just rest on their laurels.
Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.