As I sit here inside, watching the cold wind blow and snow pile up outside the warmth and safety of my little writing spot, I wonder just how all those living beings outside are surviving. Trees are swaying in the wind, and birds trying to visit the feeder are forced to alter flight plans while sporting ruffled feathers. The only animals I see are hunkered down squirrels. And just where did the insects go?
A little research tells me all of the annual plants are dead. They completed their life cycle in one year going from germinating a seed to producing seeds which are waiting winter out to make new plants in the spring. In my vegetable garden I call them volunteers. You know those tomato seeds that germinate from last year’s rotted tomato fruit that dropped to the ground and its seed volunteered to grow where I didn’t put this year’s crop. The seed survived through the winter, not the plant. Annual weeds drop seed in this manner, too.
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Perennial plants are a different story, although their seeds can do the same overwintering as annuals, the existing plant can live through the winter to grow another year, hopefully for many years more. Trees and shrubs are woody perennials that have woody above ground structures and roots that overwinter. Herbaceous perennials overwinter their roots and crowns only. The above ground portion of the plant dies back, but the crown and roots are alive at level or below ground. Perennial plants go dormant, living off of stored food until warmer weather returns. Storage organs of plants are the thick roots, rhizomes and bulbs. Just how they prepare themselves to make it through the winter happens at the cellular level long before freezing temperatures begin.
Plants are triggered by the amount of light and the amount of dark they experience, and lower night temperatures signal to get ready for winter rest and dormancy. Different species have varying light and temperature levels signals. Deciduous trees and shrubs must begin the process of losing their leaves by first stopping the production of their food. We notice it in slower growth and in the leaf color. The leaves are the food factory of the plant where photosynthesis happens. Carbohydrates are made then stored in roots and woody parts of the tree or shrub. Lots of light and water results in good growth and food storage, but when light amount lessens, leaves slow down production. Chlorophyll is also produced during photosynthesis, giving the leaf a green color. Once the leaves stop working, no more chlorophyll is produced and the other plant pigments of red and yellow are exposed now that there is no green chlorophyll to cover them. This is when we see beautiful fall foliage. The next change happens in a specialized layer of cells at the point where the leaf stem (petiole), attaches to the twig called the abscission layer. These cells enlarge and harden to choke off water flow to the leaves and the leaf slowly dies and falls off.
The next cellular change is called cold hardening. It happens within the vascular system containing the plant juices and water. If water inside the cells freeze, it will rupture the cells, permanently damaging the plant. The cold hardening process increases the sugar content of the water, and makes other protective chemicals, lowering the freezing level of the plant liquid. Basically the plant makes its own antifreeze. Cell walls are also changed to allow water leakage into spaces just outside the cell so if crystals do form, damage will be avoided. The acclimation of all these changes makes the plant able to tolerate below freezing temperatures. Fall pruning or fertilizing with nitrogen during August and September stimulates new growth interrupting the cold hardening process.
Evergreen trees and shrubs have thick leaves with waxy coatings to prevent moisture loss. Some broadleaved evergreens have gas exchange openings called stomata on the underside of the leaf. In very cold weather the leaves will curl as the stomata close to prevent moisture loss. Rhododendrons are a good example. Evergreen plants will continue to photosynthesize as long as there is moisture available, but much more slowly during the winter.
Animals and insect have the ability to move, unlike plants. They can migrate, hibernate or adapt to winter’s cold. Certain birds migrate to warmer areas and better food sources. Hummingbirds, osprey, wood ducks and song birds fly south, and some birds from far north in Canada come south to spend the winter here. Juncos, snowy owls and bald eagles summer at a higher latitude and spend the winter nearer to us. They go where they can find food.
Some animals go into a winter dormancy or hibernation. This phase consists of greatly reduced activity, sleep or rest, and lower body temperatures while their bodies are sustained from stored fat. Bears, woodchucks, skunks, bats, snakes and turtles all have true hibernation, not waking until light levels increase and food sources begin to be available again. Bears and bats find caves, woodchucks, and skunks dig tunnels, snakes and some turtles burrow into soil and leaf litter, all in protected sites.
Woodchuck at the entrance to his tunnel where he will spend the winter.
Other animals such as chipmunks have underground burrows lined with stored nuts and other food. Beavers do the same in lodges they build just above water, and line with stored logs to feed on during the winter. They sleep for long periods, only waking to eat and if maybe take a short walk above ground before returning to their den. Fur bearing animals will grow a thicker winter coat to help keep them warm, and may be a whiter color to provide camouflage in the snow.
Voles are active all through the year. In winter, they will tunnel through the snow, just on top of the ground looking for plants material to eat. They will strip the bark off of young trees and eat the roots. Voles store seeds and other plant matter in underground chambers. Mice are active and breed year round, living in any protected nook or cranny they can find, including our homes. They store food in hidden spots away from human and predator activity. Check for mice tracks around your foundation after a freshly fallen snow to see if mice are using your house for their winter quarters. Moles are active deep underground, below the frost line, in an elaborate array of tunnels. They feed on soil dwelling insects throughout the winter. I guess you could say they go ‘south’ in the soil profile during cold weather of winter.
Squirrels do not migrate nor hibernate, they adapt. They are active all winter, raiding bird feeders, and feeding on stored nuts. They grow a thicker coat of fur and fat for winter. Squirrels make great nests high in trees, well insulted with leaves. Several grey squirrels will share a nest to keep warm. They are often too quick to get a close up photo!
Insects as a group are very large and diverse. Some migrate in their adult stage such as monarch butterflies and some species of dragonflies. Others overwinter in pupal stages like the chrysalis’ of spice bush swallowtails or cocoons of Cecropia moths. Others adult and immature insects, depending on species, enter a state of diapause, similar to hibernation in animals, to overwinter during the winter. Diapause is a dormant semi-frozen state for some insects. And like plants, changes at the cellular level occur, too. These insects produce an alcohol-like chemical and added sugars to the moisture in their bodies to prevent freezing, just like vodka will not freeze when placed in our home freezers. Insects will first seek out a protected place in the soil, leaf litter or under lose tree bark or rotten logs.
The brown and orange woolly bear caterpillar burrows into the forest floor to spend the winter as in its larval stage. In spring it will come out of its dormancy to pupate, later becoming an Isabella tiger moth.
Other insects lay eggs singly or in mass groupings, which are equipped to live through the winter and hatch when conditions are good again. Gypsy moths spend the winter as egg masses, tolerating down to -20 F temperatures. Crickets are another insect group which lays eggs in the fall on the ground that will provide a new generation of night songs for us to enjoy the next summer.
Gypsy moth egg mass will overwinter on this tree bark. Hatch will be in late spring.
-Carol Quish
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