Laura Emerson
The term, “Dead of Winter” sounds negative, doesn’t it? Maybe even dire?
How about the synonym, Fall, for Autumn?
Actually, the cold season is as necessary and beneficial to plants as nightly sleep is to humans. It is a period of rest and rejuvenation. Metabolic shifts in both plants and animals during this rest phase reduce the needs for energy and food, protect cell structure and health in several ways, and prepare us both for the next day or season.
I have studied permaculture, the chemical properties of medicinal plants, and basic botany. But until I started writing this article about animal sleep and plant dormancy, I did not realize how much animals and plants have in common.
HORMONAL IMPACTS
Did you know that plants have hormones? Yes. Just as human growth and sleep periods are managed by hormones, plant growth and dormancy are similarly regulated.
For humans, melatonin is triggered by darkness and we tend to sleep better in a temperature cooler than the day. Because it is an anti-oxidant, melatonin helps with cellular repair, reduces inflammation, and facilitates DNA maintenance. It stimulates our immune system, especially by boosting white blood cell count. No wonder a good night’s sleep is important to health!
Similarly, in plants, when the hours of daylight decrease, temperatures drop and the plants receive less water, abscisic acid triggers several seasonal changes that protect the plants. Its most obvious effect is that deciduous trees and plants shed their leaves in autumn. This relieves the energy engaged during the summer to photosynthesize for growth because there is less light available.
A less obvious effect is that perennial plants shut their stomata to slow transpiration in response to abscisic acid. This means that less water moves through the plant, and the cells shrink. Otherwise, fully saturated cells would freeze, expand, and burst. It also prevents seeds from germinating until temperature and light increase. Abscisic acid allows plants to rest after a vigorous growing season.
When deciduous trees, plants, and larches (the only conifer that sheds its needles) drop their leaves (and needles), they blanket the ground around their trunks with plant material. This forms a welcome, shallow, insulating layer that has the additional benefit of degrading under the winter snow to enrich the soil. This is why raking up leaves in fall is a make-work project that does not need to be done. In fact, many organic gardeners ask friends for the leaves they choose to rake up so the gardeners can mulch their perennials and gardens.
Just as sleep helps us fight inflammation and cellular damage, winter cold causes weeds and pests to die or go dormant for a season, reducing those stresses on plants.
Obviously, nutritional needs decline during mammalian sleep as well as plant dormancy. This is because our metabolisms slow down: we do not need to expend as much energy, so we require less fuel. Hibernating bears, for example, can shed 1/3 of their weight during hibernation as they live off their fat stores. Similarly, plants need no water or fertilizer during the winter.
SNOW
Readers who live in consistently warm weather may not think of snow as an insulator, but it certainly is. The crystalline form of snow forms air pockets. Envision a snow bank as structured like insulating panels of polystyrene foam. At a temperature of 32∞F, this bank protects the roots and lower trunk of perennial plants and trees from temperatures that plummet far below that threshold. Where I live, in Alaska, at USDA zone 3b, winters always drop to 20-30∞– below 0, and occasionally, lower still. Those plants certainly benefit from snow’s 50∞ degree protection! It is common for people to shovel snow toward their buildings under the eaves, to protect the plant roots along the building and to form a snow berm “wall” to keep the cold wind from whipping under an elevated home.
Most young trees, like willow, birch, and alder, are so flexible and whippy that they bow down to the ground under the snow weight, thus being totally insulated, like a babe in swaddling clothes. As these trees age, they get stouter, with thicker bark, and are better able to withstand the brutal cold winters.
Thus, snow is for plants what a mound of quilts and comforters is to me. I, too, sleep in a cool room, with a cold nose but warmth below.
Without snow, or above it, vertical frost cracks can form in trees. They sound like gun shots! We hear a few every winter. Southern and western facing tree trunks warm during the day. At night, the temperature plummets. The warm (exterior) bark shrinks, but the inner, cool center does not, so the bark on the warm side and the wood right below it crack… loudly! This seems to be especially evident in older trees rather than young ones.
GERMINATION
Just as many animals, like moose and deer, mate in autumn to bear young in early spring, a number of cold weather plants can actually be planted in the fall, before soil freezes, in order to take advantage of early spring thaw, leafing out through shallow snow. Another set of plant hormones, called gibberellins, triggers the temperature cue for germination, which varies. Among leafy plants, spinach and lettuce are two that can sprout very early. Root vegetables like garlic, onion, beets, are well acclimated to autumn planting for early spring leafing. In my very snowy climate, however, many of these fall- planted seeds can rot in the snow melt. So, I often winter-sow these seeds in containers and leave them outside all winter, putting them in a sunny spot in February/March for transplantation when the snow recedes and the gardens dry up a bit. Most plants, though, germinate at higher temperatures.
TRICKY WEATHER
Just as people can wake up in the middle of the night due to some sound or dream, and start their day at, say, 3 am, only to crash early the next day, so, too, plants can inopportunely “awaken”. An unexpected warmth spell (up here, perhaps caused by a strong Chinook weather system that can raise the temperature by a huge margin) can trigger spring behaviors. Leaves sprout, flowers form, only to be killed by the next dash of low temperatures. The vicissitudes of weather are particularly detrimental to domesticated plants. Local wild ones have had more generations to adapt.
Recognizing these similarities between humans and plants gives me greater sense of affinity with them. Although our deep snows and cold temperatures can challenge me, I now view them as beneficial to the boreal forest that surrounds me. Maybe in addition to familial terms like Mother Nature, I will start thinking of additional relationships, like Brother Tree and Sister Flower.
Author: Laura Emerson lives off-grid with her husband in the Alaska bush – population 4 – a 20 minute flight from the nearest road. Curious about such a life? See Log Cabin Reflections on Amazon for $5. Lots of pictures and anecdotes, arranged by season.