Winter Sleep and More

Perhaps it was the recent attention to daylight savings time, along with the shortening days and increasingly bare tree limbs, that got me thinking about winter sleep. Bears are  known masters of sleeping away the cold season but what about the rest of us: humans, other animals and even plants?

Much has been written about the need for sleep. Not getting enough means the brain doesn’t have time to recharge its batteries and grumpiness is sure to follow. People tend to sleep more in winter than in any other season as the brain has less access to sunlight. This directly impacts the pituitary gland. The extra amount of melatonin it secrets in response means the owner is being signaled earlier in the day it is time to sleep.

But what about God’s other creations.  Plants? Do they sleep? At some point in the 1700’s the storied botanist, Carl Linnaeus found that flowers kept in a dark cellar still opened and closed regularly, as though they were expecting sunlight and shutting down when it was due to disappear. The equally storied Charles Darwin noted a century later that the nocturnal movement of leaves and stalks suggested the plants were sleeping but that was misleading. He thought such flowers as tulips, hibiscus, poppies and crocuses that close at night are simply defending themselves against the cold. (The process has the inglorious name of nyctinasty.)  

But what about trees, those big sky piercing plants that rule the landscape?  Are they tired after photosynthesizing all day and only wish to fall asleep at night? It turns out sleeping is too generous a term but “dozing’ is not. Scientists monitored two silver birch trees (Betula pendula), one in Austria, the other in Finland, using laser beams to measure the height of the branches and leaves from the ground. The measurements continued from dusk to morning in September when the days and nights are of almost equal length.

What the researchers reported was that the branches and leaves sagged about 4 inches at night, reaching their lowest levels a few hours before sunrise, and then perking up again to regain their original position. It is as if the tree has its own circadian rhythm. We cannot know from current information if the birches would “doze” longer in the cold weather, when the days are shorter, but an educated guess would be that they do. (Every other plant that beds down for the winter comes back fresh in spring, suggesting a  fruitful rest and recharge.)

Unlike trees (and bears) the human species has a few more options when negotiating the cold season. All the same, I am attracted to the idea that we tend to brumate above all else; a fancy way of saying we are one level above hibernation. Like coldblooded lizards, we seek out a warm place to hide till things warm up. In the meantime we remain in that spot a touch lethargic.

I am of the admittedly biased opinion that gardeners have an advantage under such a scenario. Namely, they can read seed and plant catalogues for the next season while they are droopy in the dark. So when they go to sleep earlier than they would in the summer they can dream about what is promised when they start gardening again.

Of course, there are always other ways to break out of this lethargy. Coming to the Winter Solstice celebration December 9 (I know it is early) would be one way of doing so. This is the outright favorite event for members and guests in the whole year. It begins at 5:00 pm when it is getting dark. Visitors are welcome to take a candle and walk the Celtic Circle in its soft light, to think about the past year and the one to come. Even Benjamin Franklin, I am sure, wouldn’t mind the burning of the lights. It was he who proposed daylight saving as a way to save expenditure on candles in the winter. 

Image by Jennifer Willis




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