With fall leaves past peak and a heavy weekend frost, many a gardener will hang up their hat for the winter. But, do not despair dear gardener! Not all is lost in the garden, especially when it comes to vegetables. Did you know that the brassicas such as kale, collards and other hardy greens get sweeter after a frost?
Plant have a lot of water in them, and when water is exposed to freezing temperatures it becomes ice. If you can imagine, the creation of ice crystals inside of plant tissue wouldn’t be good for the overall health of the plant – jagged edges would burst cells, creating leakage and subsequent lack of water … kind of like a limp leaf of lettuce. This bursting of cells explains why it’s not a good idea to freeze lettuce or other sensitive leaf tissues, since there’s no coming back when cells have burst.
Processes to protect the bursting and dehydration of plant cells under cold temperatures are varied and complicated, and science hasn’t been able to come up with an easy answer yet. However, a few ideas persist, one of which benefits winter vegetable eaters. Plants develop solutions similar to antifreeze within the cells to prevent water from freezing in the first place, and these solutions tend to taste sweet.
Kale and hardy brassicas can withstand freezing temperatures of 25 F. If you use mulch, cold frames, or row covers, you may be able to protect your plants at even lower temperatures. So, enjoy your frost-kissed kale for a few more days! It will taste sweeter because of it.