This week for Flora and Fauna Friday we have a festive forest fern, Christmas Fern (Polystichum acrostichoides).
Christmas Fern is a species of evergreen fern found across the eastern United States and practically all of South Carolina. Its deep, jade-green fronds are divided once, giving the frond a feather-like appearance. The pinnae that make up the frond are glossy, lightly toothed, have a characteristic lobe at the base that points back to the ground, and sparse, orange hairs along the stem. The spore-bearing sori on the underside of the frond present predominantly as two parallel lines of cinnamon spots. The fronds of Christmas Fern are roughly forearm length, emerging at an angle from the ground and held low like a shallow basin shin-high above the ground. Christmas Fern is perennial and will spread slowly through its roots underground, most often forming loose clusters of clumps. Christmas Fern gets it holiday name from its evergreen foliage, which stays green throughout winter. This makes it a favorite addition to festive wreaths and arrangements over the holiday season.
Christmas Fern is a denizen of deciduous forests, damp soils, and deep shade. I most often find it around South Carolina growing in creek valleys, above stream banks, on north-facing slopes, along hillside seeps, between the buttresses of oaks, and just uphill of wetlands. Here around the Sea Islands, I mostly see it in the ecotone, the transitional band of land between ecosystem types, where mixed-hardwood upland forests grade downhill into swampy bottoms, especially when downhill faces to the north. That north facing slope is important. Here in the temperate zone of the northern hemisphere, the sun is always in the southern half of the sky. Meaning slopes that face south get more sun, and slopes that face north get less. The soils of those north facing slopes thus stay in shade for much of the year and dry out less. Perfect conditions for our shade tolerant, moisture loving Christmas Fern. This effect is far stronger in the Upstate. Yet here in the Lowcountry, where elevation is measured in inches, it can still have a significant impact within a forest. Christmas Fern is a species that doesn’t tolerate disturbance well. It prefers established, mature, deciduous forests. For me, as an ecologist, that makes it a useful indicator species for intact forest ecosystems. Where I find Christmas Fern in the Lowcountry, I know I’m in a healthy forest, a place worth protecting, and to be on the lookout for rarer plants and animals.
