When it gets cold, plants have ways to adapt
- Herb Broda: Nature Notebook
- November 19, 2020
- 1329
We know a lot about how animals survive the winter — they either hibernate, migrate or adapt. But how do plants make it when the temperatures drop below freezing for days at a time?
Plants don’t hibernate and they certainly don’t migrate (although it is fun to imagine a gang of hostas heading south along the interstate). That leaves adaptation. And plants have definitely developed some amazing ways to adapt to sub-freezing temperatures.
Some plants don’t protect above ground structures from the cold. Instead, they rely on underground storage organs such as tubers (potatoes), tap roots (carrots) and bulbs (garlic) to store food over the winter. In the spring, the stored food provides the energy to grow new shoots and leaves.
Many other cold-tolerant plants cope with frigid weather by entering a period of dormancy. According to the University of New Hampshire Extension Service, dormancy is
triggered by hormones that are activated by changes in the angle of the sun, amount of daylight and cooler
temperatures.
Many plants create their own type of antifreeze. By accumulating sugars, salts and other substances plant cells can control when and where freezing takes place. Cells also can change the permeability of their membranes, allowing them to concentrate their “antifreeze” where it’s needed most.
The New Hampshire Extension folks point out that this “antifreeze mechanism” is most effective for many perennial plants when the temperatures’ are in the 20-32 degree range. Long periods of deep cold can still do significant damage.
Both soil and a blanket of snow can serve as good insulators. The ice crystals in snow have air space between them which serves as insulation for the soil beneath. Even if the temperature nears zero, a good layer of snow can keep the soil temperature near 32 degrees.
This stabilizing effect is especially important if there is a brief winter warm-up. The snow keeps the soil at 32 degrees thereby avoiding the premature sprouting of seeds.
Winter Lore
Recently I made an impulse buy of the The Old Farmer’s Almanac for 2021. It’s always fun to see the almanac’s weather predictions and then watch as the season plays out. The prediction for this December is for average temperatures to be above freezing with above average precipitation.
It’s interesting to match that with a colorful piece of old farm weather lore from my friend and Amish farmer, David Kline: “If a horse can walk on the ice in December, a dog won’t be able to walk on the ice in January.”
If the almanac is correct, and David’s adage holds true, there won’t be any horses walking on ponds next month. But does that also mean that dogs will be romping on the ponds in January?
Green Bean Trivia
Regardless of the weather, the approaching holidays turn our thoughts to recipes that are lastingly linked to our celebrations. One of my favorites is the green bean casserole.
The story goes back to the 1950s, a time when convenience cooking was very much in vogue. As more and more women entered the post-war workforce, recipes for easy to prepare meals became very appealing.
The folks at Campbell’s Soup saw the changing workforce as a way to accelerate sales of its canned soups. More soup could also be sold if soup was not just a separate meal item, but also a key ingredient in easy to prepare recipes.
According to History.com, Cream of Mushroom soup was widely used as a casserole ingredient soon after its introduction in 1934. In fact, it appeared in so many Midwest casseroles that it was “sometimes referred to as the ‘Lutheran Binder.’ Although the soup was popular, it never was promoted in recipes that also featured green beans.
That changed in 1955 when Dorcas Reilly, a supervisor in the test kitchen at Campbell’s Soup, created a recipe based upon two simple ingredients already found in most kitchens: green beans and cream of mushroom soup. The recipe could be prepared ahead and then reheated which definitely increased its popularity as a holiday side dish.
Although it’s difficult to calculate, the company estimates that 40 percent of its cream of mushroom soup sales go into one dish — the legendary green bean casserole.