On this Winter Solstice, the forests are now colored in various shades of tan and brown here in southern Connecticut. But here and there are patches of green. Whether they signify rebirth, a new life, immortality, or peace, plants that are still green have played an important role in almost every holiday celebration, particularly during the winter.
Plants that remain green in winter can still photosynthesize using the sun’s light plus water to produce sugars to “feed” themselves.
How are these plants able to stay green and keep from freezing? Cold stress is just as lethal to plants as heat stress. When water inside the cells freezes, it expands, causing the cell membranes to burst and the cells (and plant) to die.
Many plants in winter respond to colder temperatures by accumulating sugars and moving them to the leaves. Those sugars lower the temperature at which ice forms—like putting salt on the roads.
Another adaptation plants have evolved for protection in winter is to make proteins. This helps to stabilize cell membranes and keeps them from bursting.
We’ve had several nights below freezing and yet the Pansies (Viola spp.) in my window box are still green and in flower! I think, though, it is just a matter of time before freezes will kill the Pansies, so I’ll soon be moving them to the porch.
Look for evergreen ferns on your next winter hike. I say evergreen, but no plant is truly evergreen. Plant leaves and fronds eventually die and are replaced. Marginal Wood Fern (Dryopteris marginalis) and Christmas Fern (Polystichum acrosticoides) are two ferns that are easy to find now and throughout the winter. They are often seen growing near one another.
Marginal Wood Fern is a light blue-green with broad, twice-compound leaf blades (divided into leaflets that are further divided into more leaflets). The Christmas Fern is named because its dark, leathery leaves are green at holiday time, and because each of its leaflets are lobed like a Christmas stocking.
Patches of these ferns provide winter cover near the ground for songbirds. Some bird species use parts of the fern’s scale-like hairs to build nests come spring.
Both of these plants feel rather waxy to the touch—yet another great adaptation for protecting leaves in the cold. Many coniferous, or cone-bearing, trees have waxy leaves or needles too. Coniferous trees and native, broad-leaved evergreens such as Mountain Laurel (Kalmia latifolia) and Inkberry Holly (Ilex glabra) are very important for birds and other wildlife in the winter. These plants provide shelter from harsh winter winds and protection from precipitation.
If you see what looks like miniature pine trees growing in a line on the forest floor in winter, you’ve found one of the clubmoss species, an ancient line of fern relatives in the genus Lycopodium, Dendrolycopodium, Diphastiastrum, or Huperzia. Nicknamed ground pine or running pine, and only a few inches off the ground, the ancestors of these plants during the Jurassic Period were more than 100 feet (30.5 meters) tall! Please don’t cut club mosses for holiday wreaths. The plants grow very slowly and local patches can be wiped out by collecting.
Even though I know we’re in for more frigid temperatures, I look forward to the increasing light of longer days from here on. The winter’s greenery invites you to look forward to spring.
Wishing you peace and a healthy, prosperous New Year.