Some plants handle winter better than others, while others can’t handle the cold at all. And winter in central Florida is a whole lot different from winter in central Wyoming. Brrr!
How plants protect themselves from cold weather is pretty fascinating. And you may be surprised at the number of plants that can withstand the cold.
How plants react to cold
Most vegetable plants react badly to freezing temperatures. The moisture held within each plant cell expands as it freezes and those cells rupture.
From the outside, we see blackened leaves and stems that indicate decomposition has begun. But there are degrees of cold. And the conditions that exist before temperatures drop to freezing matter, as well.
Degrees of cold
Just as water droplets will condense on your glass of summer iced tea, plant surfaces also collect dew on their surface. When temperatures drop below 36°F, that dew becomes frost. Frost can be light (28°F-32°F) or hard (below 28°F).
As temperatures drop, some winter-hardy plants protect themselves by producing more sugars. This is why cabbages and many other crops are sweeter after a light frost. The sugar lowers the freezing temperature of the water held within, making the plants more cold-tolerant. [I just read an article about how sugar beets are being used as road deicers instead of salt as a method of protecting the environment while keeping our winter roads safer.]
The condition of the plants before freezing also makes a difference. Plants grown in warm temperatures that are suddenly exposed to a hard frost will usually die. Those same plants, exposed to gradual cooling over time, can tolerate surprisingly low temperatures.
Plants that tolerate cold
Many plants that grow from bulbs and corms can withstand bitter temperatures. Tucked away safely in the soil, saffron crocus plants often send up green shoots before the snow even melts. What these plants can’t tolerate is excess moisture. Cold, wet plants tend to rot in the ground.
Before cold weather hits, you will want to harvest everything that will be ruined by frost. Common garden plants that are damaged by a light frost include:
While these plants are often made sweeter with a light frost:
*Winter hardy lettuces are planted close together and are often called "winter density" lettuces.
And these plants can tolerate a hard frost:
Did you know that greens such as kale and spinach with savoyed, curled, or textured leaves are more cold-tolerant than smooth-leaved varieties? Now you know.
Most of your fruit and nut trees will produce bigger and better harvests because of the cold as they collect chill hours throughout the winter.
Protect your garden from winter cold by giving it a blanket of aged manure and compost or a layer of straw mulch. All those tiny air pockets will act as a cold buffer. And be sure to drain those garden hoses and drip irrigation systems. You can protect frost-sensitive plants by covering them with a tarp, sheet, or umbrella. Just make sure that the cover doesn’t touch the plant or it won’t work.
You can always extend your growing season and protect frost-sensitive plants with hoophouses, row covers, and cold frames.
How cold do your winters get? Your USDA Hardiness Zone can answer that question.
Kate Russell, writer, gardener, and so much more.