An enduring favorite of mine among Vineyard plant species is sweet fern, Comptonia peregrina, now coming into leaf in an open area near you. While it is not one of those powerhouse plants, like the members of the oak family, that support entire ecosystems, this hardy shrub proves useful to some other species. And I admire the plant itself for its intrinsic ruggedness.
Its common name notwithstanding, sweet fern has nothing to do with true ferns. The common name comes from the shape of sweet fern leaves, which are elongated and notched on the edges, like the leaves of ferns. But taxonomically, Comptonia is in the family Myricaceae, along with bayberry and sweet gale.
Like those relatives, sweet fern has aromatic leaves and flowers, and part of my fondness for this plant stems from my long familiarity with that scent. I figure I was 4 or 5 years old when introduced to it, and it would have been my father who crushed a leaf and gave it to me to smell along a powerline cut near our home in Lexington.
The leaves and flowers of sweet fern can be incorporated into potpourri, and have long been used as a traditional remedy for digestive and pulmonary ailments. Whether the purported medicinal effects are real, I can’t say, but this plant certainly smells like it should be beneficial.
My introduction to sweet fern along a powerline cut is no surprise. This is a plant of sunny, dry, waste places, often ones with lean, shallow, and acidic soils. On the Vineyard, suitable conditions for and sizable populations of this plant can be found along the powerline cut that runs inland along West Chop, and also in portions of Correllus State Forest.
Sweet fern is easily recognized by the fernlike foliage mentioned above. It’s a deciduous perennial shrub featuring a shallow, spreading root system — characteristics that make it useful for projects such as stabilizing loose soil or establishing vertical structure in landscaping. Never a tall plant, sweet fern spreads mainly by rhizomes, and tends to form fairly dense stands, with all the plants of a uniform height of two or three feet.
As one would expect, the habitat preference of this plant is matched by the plant’s physical characteristics. In addition to being aromatic, sweet fern leaves are tough and leathery when mature, sporting a thick cuticle that helps retain water under sunny and droughty conditions. And that spreading root system lies in wait close to the surface of the soil, snaffling any rain that infiltrates the ground.
Moreover, as is the case with beans and other legumes, sweet fern has a symbiotic relationship with a bacterium that allows the plant to fix its own nitrogen, effectively fertilizing itself. This relationship lets sweet fern flourish in soils too lean and sandy to support most other plants.
Like many plants, sweet fern can be a bit too zealous when it’s happy, spreading aggressively and crowding out other species. But individual stems are relatively easy to yank out, and you can often keep yanking on a rhizome to pull multiple stems at one whack. So even where it’s mildly invasive, it is generally easy to discipline with once-a-year uprooting sessions.
While the leaves of this plant presumably evolved their pungency in part as a measure to discourage herbivores from eating them, sweet fern is fed on (more in winter than in summer, apparently) by white-tailed deer and rabbits. The seeds of sweet fern, tasty but tiny little nuts, ripen in late summer inside burrlike fruits, and are edible. Birds undoubtedly eat them (flickers, oddly, seem to be one of the few species actually documented doing so), and humans can, too, although I’d hate to have my survival depend on gathering the tiny seeds in significant volume.
In late April and early May, sweet fern blossoms, producing separate male and female catkin-like flowers (often but not always on separate male or female plants). Sweet fern is primarily wind-pollinated, with male flowers dumping billows of pale, yellowish pollen into the air. Personally, I don’t find sweet fern pollen at all irritating. But results may vary, and the allergy-prone might want to avoid walking through clumps of this shrub when the plants are in flower.
Wind-pollinated plants, of course, don’t require pollination by insects, and I had always assumed that sweet fern is of no interest to bees and other pollinators. But one keeps learning: So far this spring, I’ve seen three species of bees representing three separate taxonomic families ardently collecting pollen from male sweet fern flowers.
I can’t find any information on the nutritional value of sweet fern pollen. But bees are experts at being bees, and if they’re collecting the pollen, it’s because they are confident their larvae will benefit from eating it.
Common if patchily distributed on the Vineyard, sweet fern is worth keeping an eye out for. Tough, distinctive, and useful to its neighbors, it’s a good member of the Island community.