The pansies on our front porch easily survived the winter of 2017-2018 and during the cold weather, grew and flourished. Why does this happen with pansies and very few other flowering plants like tomatoes and peppers? How do pansies survive for eight hours in ten degree Fahrenheit temperatures? David Goforth, agriculture extension agent for the North Carolina Cooperative Extension Cabarrus County Center, says the condition centers around three facts.
The first fact is that plants die from ice inside the cells. The ice inside the cell punctures the cell wall. Ice between the cells doesn’t kill the cells. Ice on top of the plant surface doesn’t kill the cells. The second thing happening in a pansy is osmosis—the passage of water through a semi-permeable membrane, like your skin wrinkling in a bathtub. Finally, the more impurities there are in a solution, the lower its freezing point.
So here’s how it happens. Ice forms between the plant cells in the pansy. As the pure water freezes, it changes the solution outside the cells. Water moves from inside the cells to outside the cells by osmosis. This water also freezes between the cells. More water moves out. It also freezes. The remaining solution inside the cell has a higher concentration of sugars and other impurities so the inside of the cell doesn’t freeze. With no ice inside the cell, the plant lives. Goforth ends his explanation with a comment that I agree with: “Why we use this plant name as a synonym for an effeminate male is beyond me.” As I said, pansies are tough.