What is a native plant enthusiast to do during our region’s long dormant season? While half of the year delights us with new growth and flowers, the other half can test our patience as we wait for spring. Some of us occupy our minds with twig identification. Others puzzle over the withered remains of once familiar herbs. Those with a penchant for chemistry may take up lichenology. But greenness is what I crave, and the muted tones of conifers simply don’t suffice. So, for solace, I turn to the swamps and scout for the promise of summer among the mossy hummocks.
Except in times of deep snow, the dormant season provides advantages to swamp-walkers. After the frost has done its work, there are no buzzing or biting insects. The crowds of forbs subside, clearing the way for a broader view of the forest floor. Then comes a good freeze, and the wetland’s mucky mire becomes as easy to traverse as the uplands. An early dusting of snow – what I call “tracking snow” for another favored winter activity – is just enough to highlight evergreen herbs, making them stand out in sharp contrast to the whitened blanket of mosses.
Under such conditions I have found many uncommon or otherwise hard-to-see evergreen plants. Some of these species are indicators of soil rich in nutrients, which also signifies special habitat that can be rich in botanical diversity. A return to these places during the green months may reveal a bounty of other species, including such prizes as showy lady’s-slipper (Cypripedium reginae) and other orchids.
Here are three examples of evergreen plants I’ve encountered during dormant season swamp walks. These species are relatively easy for new botanizers to identify, especially when competing vegetation has died back for the season. Each is also an indicator of special habitats that warrant summer visits.
Naked Mitrewort (Mitella nuda)
Despite its name, naked mitrewort does indeed have some foliage to clothe its plant body. The “naked” refers to its leafless flowering stem, in contrast to the more common bishop’s cap, or two-leaf mitrewort (Mitella diphylla), which, as its name indicates, has two leaves along its flowering stem. The foliage of naked miterwort occurs along a creeping horizontal stem (stolon). These spread along the ground as well as through mounds of moss and rotting wood. Naked mitrewort leaves are small (usually about an inch wide) and somewhat kidney-shaped, with scalloped leaf margins and short, stiff hairs on the upper surfaces. Colonies of this plant are patchy; they don’t exactly form a carpet of ground cover but rather dot the hummocks like sprinkles on cupcakes.
Of the three species included in this profile, naked mitrewort is the strongest indicator of rich wetlands because it only grows in this habitat. You’re most likely to find it in places with calcium- or magnesium-rich bedrock. Black ash is a characteristic associate, and northern conifers such as arborvitae, balsam fir, and tamarack can be dominant species at these sites (but may also be entirely absent). Naked mitrewort is also a plant of cooler climates. In several populations I’ve seen at the edge of its range in southern New England, colonies were small and flowers sparse to absent. These are common signs of decline, and marginal populations like these can serve as early indicators of climatic stress affecting other components of an ecosystem.
One-Sided Shinleaf (Orthilia secunda)
This is a close relative of the more familiar shinleaf plants in the genus Pyrola. As its name reflects (secund means “one-sided”), Orthilia is distinguished from Pyrola by its strongly one-sided inflorescence (flowering stem). Conveniently, this is also its most conspicuous winter feature; the stalks of dark brown capsules stand out against a backdrop of snow. Plants occur in colonies connected by underground rhizomes. Tufts of foliage emerge along the rhizomes, with flowering stems emanating from their centers. The vibrant green leaves are egg-shaped with a toothed margin, impressed veins, and bluntly pointed tips, somewhat resembling the leaves of apple trees.
There are many old herbarium specimens of one-sided shinleaf from across a surprisingly wide range of habitats where it is no longer found, especially in southern New England. Importantly, one-sided shinleaf is partially mycoheterotrophic, meaning it gets at least some of its carbon and nutrients via an obligate fungal associate in the soil. As with many other mycoheterotrophs, including orchids and several other shinleaf species, one-sided shinleaf has been declining across its range. Possible factors contributing to these declines include nitrogen deposition, climatic shifts, and loss of young forest habitat, which singly or in combination affect the plants or their fungal associates. Thankfully, rich conifer swamps remain a stronghold for one-sided shinleaf in the Northeast.
Dwarf Scouring-Rush (Equisetum scirpoides)
Even among the horsetails, dwarf scouring-rush is an oddball. Unlike the tall, erect stems of more common horsetails, its slender, wiry stems form ankle-high, dense tangles resembling steel wool. Closer inspection reveals classic Equisetum characteristics, including pointed, spore-bearing strobili and papery black-and-white teeth sheathing the stem nodes. Dwarf scouring-rush grows in a wide range of habitats, but it is most stable in wet, shady coniferous settings, particularly in rich, clayey, or silty soils. It can form extensive colonies on bare mineral soil, so it thrives with some periodic soil disturbance, such as wind-throw or landslides. Other common growing sites include rich, moist northern hardwood forests and disturbed soil around spring seeps. Dwarf scouring-rush is generally a more northern species, so sites need to stay cool enough for plants to persist. Toward the warmer end of its range, in southern New England, populations grow mostly in deep shade, at high elevations, or on steep, north-facing slopes in ravines.
One of my most exciting January botany successes involved all three of these species in a high-elevation conifer swamp in Berkshire County, Massachusetts. The swamp forest was composed of red spruce, balsam fir, black ash, and tamarack. I first visited the site in late fall, where I discovered naked mitrewort and one-sided shinleaf growing abundantly on the mossy hummocks at the bases of trees. After an unusually snowless winter, I returned to the frozen swamp following a fresh half-inch of snow. In the same places I had walked before, I was able to document a large population of dwarf scouring-rush, easily detecting the wisps of crinkled stems over a broad area. Returning again in summer, I’ve found uncommon species including wild red currant (Ribes triste), hemlock-parsley (Conioselinum chinense), and the north-wind bog orchid (Platanthera aquilonis). I’ve heard that other visitors have found showy lady’s-slipper there in the past, proving there’s always something more to look forward to – and something green to dream of through winter.