The Christmas Fern: a Fern for All Seasons
I take pleasure in the muted palette of the winter woods: the sepias and silvery-grays of tree bark, the faded ocher of leaves fallen or still clinging on, the soft violet of shadows upon snow. Still, I crave green as much as the next person in late winter, and while walking our wooded uplands, my eyes gratefully pick out gray-green lichens, lime-green mosses, and the glossy bluish green of the Christmas fern.
The Christmas fern, (Polystichum acrostichoides), so-called because its evergreen nature once marked it for use as indoor greenery during the winter holidays, is the only truly native evergreen fern in our area. It is the most common fern in Indiana—indeed, the most abundant fern in the eastern U.S. and Canada. It is hardy as well as ornamental, modest in its requirements, and relatively pest-free and deer-resistant. It is usually available online and at nurseries and garden centers, and is a mainstay of native plant sales. In short, it is a prime fern for the shade garden.
In the wild, Christmas fern is not overly fussy about its habitat, bordering streams, clinging to rocky banks and hillsides, and clustering at the base of trees. In southern Indiana it even keeps company on the drier ridgetops with chestnut oak, painted sedge, low-bush blueberry, and a dainty but sharp-tasting mint called dittany. Christmas fern grows in subacid to nearly neutral soil, including clay, and is quite heat-tolerant. It transplants well, and is content if provided with a seasonally moist but well-drained site in partial sun to full shade.
In early spring, nestled among the flattened but still green fronds of last season, new Christmas fern fiddleheads appear, “curled up,” as Frances Theodora Parsons observes in How to Know the Ferns, ”like tawny caterpillars.” Allow these fiddleheads to unfurl and fully expand before removing last year’s tired fronds; overzealous tidying may stunt the plant’s future growth. Better yet, simply let the old fronds be. They will decay by autumn, adding to the beneficial leaf litter that sustains the wild garden.
The Christmas fern is a staunch clumper, but does produce offset plants that after one over-wintering may be divided from the mother fern and transplanted. The fern can also be propagated from spores. The mature Christmas fern produces two types of fronds: the broader sterile fronds that are first to emerge, and in late spring taller, narrower fertile fronds. Rows of round fruit-dots crowd the underside of leaflets at the tip of these fertile fronds; each dot, or sorus, is jam-packed with tiny spores. The process of harvesting these spores and shepherding them on their journey to becoming new ferns is a rather fastidious but fascinating process, described on the websites of The American Fern Society and The Brooklyn Botanical Gardens, and in William Cullina’s Native Ferns, Moss, and Grasses. Successful propagation will reward the gardener with a plethora of new ferns plants.
When considering the ground floor of a shaded landscape, why not abandon the tedious monocultures of the Euonymous winter creeper and Vinca, and look to the rich local woodlands for inspiration. The Christmas fern is lovely combined with spring ephemerals, and long after the bluebells and trilliums have faded, its leathery blue-green foliage adds texture and depth to the verdant mosaic of the summer shade garden. Combine the Christmas fern with other natives: the lacier lady, fragile, New York, and maidenhair ferns, the robust Dryopteris ferns, and the broad beech fern that appears fresh well into autumn.
Plant among them the ground-hugging woodland stonecrop (also evergreen) and the low-growing wild ginger, both excellent native groundcovers. Goldenseal, may-apple, jack-in-the-pulpit, white baneberry and woodland poppy all retain their leaves into summer and add to the multiplicity of forms. In autumn the Christmas fern is still going strong and green, bolstering by contrast the red of jack fruits, the vivid blooms of blue-stemmed and zig-zag goldenrods, the delicate blue flowers of arrow-leaved and Short’s asters.
With such a diversity of native plants the groundscape comes to life. A variety of flowers attracts pollinators and caterpillars. Birds eat the caterpillars, as well as seeds and fruits that are also relished by small mammals and box turtles. The Christmas fern plays its part in the living garden, trapping leaf litter and moisture beneath its fronds (both old and new),and creating protective cover and habitat for toads, salamanders, and other seldom seen but invaluable dwellers of the forest floor, and even subfloor.
In late winter the fern may dull a bit, but can maintain a fresh appearance if nestled in a bed of moss or other moist place. How fortunate that the Christmas fern is so easy to grow; that its year-round beauty, as well as its function in the sustainable wild garden, is so effortlessly attained. Its persistence in the dormant landscape, whether in our woods or gardens, is a respite for winter-weary eyes, and whets our appetite for the burgeoning greens to come.