Our Minnesota winters can be quite cold and snowy! We have warm houses and heavy coats and mugs of hot cocoa to keep us cozy all through the winter, but what about all the living things outside? How do they make it through the cold season?
Animals who live outdoors don’t have buildings or mittens, but they do have their own winter survival tricks. Squirrels and rabbits build warm nests, bears and frogs will hibernate, and insects and birds often migrate, flying south to warmer places for a vacation until spring returns to Minnesota.
Without arms to burrow into the ground, wings to fly away, or arms to build nests, which of these tricks can plants use to survive winter? How do plants survive the cold? Believe it or not, plants use many of the same tricks that animals use.
Let’s look at three examples.
SQUIRRELS
You might spot a squirrel on a cold winter day, running to one of its many hiding spots to find a few nuts or seeds to eat. They enjoy lazy winters, mostly snug in their nests or out on a food run, because they worked all summer gathering food and bulking up their nests for the winter.
Which plant is like this, alive and active through the winter?
A. Deciduous trees, like maples or oaks
B. Tender bulbs, like dahlias
C. Evergreen or coniferous trees, like spruces or firs
D. Hardy bulbs, like tulips
If you said C — Evergreens, you’re correct! Evergreen trees continue to be active throughout the winter, just like squirrels. They keep their green needles all through the winter months because they’re coated in a waxy shell that protects the water inside each needle. Furthermore, their roots can keep growing deep in the earth because the soil four or five feet below the grass isn’t frozen.
FROGS
If you have frogs in your garden in the summer, you will notice that they go away in autumn. As our Junior Winter Garden Detectives might remember, frogs survive winter by going into a deep sleep called hibernation, and they also make a special kind of antifreeze liquid in their bodies that keeps them from freezing solid.
Which plant is like this, going to sleep but not freezing?
A. Deciduous trees, like maples or oaks
B. Tender bulbs, like dahlias
C. Evergreen or coniferous trees, like spruces or firs
D. Hardy bulbs, like tulips
If you said A — Deciduous trees, you’re correct! Deciduous trees don’t disappear completely like frogs, but their leaves certainly do! A maple tree will drop its leaves in autumn because they are too delicate to survive the winter. The deep sleep that trees go through is called dormancy instead of hibernation. As for that antifreeze liquid that the trees make in winter to keep from freezing? You have probably eaten it on pancakes, because it’s maple syrup.
CANADA GEESE
It’s hard to miss Canada geese on our lakes in the summer. It’s even harder to miss them when they fly south in autumn, honking noisily in their V-shaped formations in the sky.
Which plant is like this, leaving the cold for warmer climates?
A. Deciduous trees, like maples
B. Tender bulbs, like dahlias
C. Evergreen or coniferous trees, like spruces
D. Hardy bulbs, like tulips
If you said B — Tender bulbs, you’re correct! You might have even been with the gardening grownups in your life when they dug up all their tender bulbs at the end of summer. These bulbs cannot fly to Florida for the summer, but go instead to the warmth of a garage until it’s time to plant them again the following May or June.
You might have noticed that we didn’t have any animal examples for hardy bulbs. Why is that? Well, this last winter trick for plants is quite unique—vernalization.
“Vernal” is just a fancy Latin way of saying “spring,” so vernalization is about the process plants go through to get ready for spring blooming and flowering. We’ve already seen that some flowers, like tender bulbs, just aren’t tough enough to survive the snowy winter and need to be brought inside.
What about the plants that are strong enough to survive the winter? This includes hardy bulbs, but also apple and cherry trees and many vegetables like cabbages and carrots. Their flowers are all ready to produce another blossom in fall, but they don’t. The cooling weather puts a flower blocker onto the plant that stops new flowers from growing. (If you have cherry or apple trees, you can go outside and see the buds that have formed but not bloomed.) What removes the flower blocker? Several weeks of cold weather. By the time the cold weather has removed the flower blockers, it’s springtime—time for new flowers to start to appear!
DO:
Try These Experiments
FREEZER EXPERIMENT on deciduous and evergreen leaves. Gather an avocado and a piece of lettuce or spinach. An avocado has a waxy outer shell like a spruce needle, and a piece of spinach is unprotected like a maple leaf. What do you think will happen when you put them in the freezer for 24 hours? For a week? Write down your hypotheses on a piece of paper. Next, place both in your freezer. Check on them at 24 hours and again at one week. What has changed? Now let them thaw out on your kitchen counter. Which one has survived the cold best?
VERNALIZATION EXPERIMENT in the garden. If you grow carrots in your garden in the summer, try leaving a few in the ground in the fall. (This will be difficult, since homegrown carrots are delicious.) A beautiful white flower that looks like Queen Anne’s lace will be awaiting you. By letting this biennial plant live out its second year, you are witnessing vernalization—the flower blocker has been taken off by winter, and now the carrot flowers are in full bloom.
Further reading and listening for adults on vernalization, both from vernalization expert Dr. Richard Amasino from the University of Wisconsin-Madison:
https://grow.cals.wisc.edu/deprecated/food-systems/winter-awakens-spring-flowering
https://www.youtube.com/watch?v=hcvmlYroJ1A
Photo credits: Pix4 Free (1), Pixnio (2)