Protecting plants from extreme weather is one of those chores that gardeners both love and loathe. We all know that some plants can’t survive cold weather on their own, while others seem to winter quite well outdoors or even thrive when the temperatures drop. So what’s the difference? Why can some plants tolerate cold weather while others can’t? The science behind how plants have adapted to different weather conditions is fascinating, and learning a bit more about it can help us understand how plants survive winter and why some plants just don’t handle the cold. Let’s dig in!
Cold Temperatures = Dormancy
Plants evolve to thrive in a particular set of circumstances, and plants that live in colder climates have adapted to those climates by finding ways to adapt to the cold. For many of these colder climate plants, this involves a form of hibernation or dormancy. Like some animals in winter, these plants effectively “go to sleep” and hibernate until things warm up and conditions are easier for life and survival. The way they do this involves a few physiological changes in how the plant handles its nutrition and internal structures.
Roots perform many functions in plants, anchoring them in the ground and gathering nutrition and water from the soil. Roots may also serve as a store house of energy and nutrition, particularly during colder weather months. By relying on the cache of nutrients, sugars, and starches in the roots, plants can effectively rest during colder weather when they can’t photosynthesize as much energy from their leaves and other green parts. In some plants, the roots continue to gather moisture and nutrition throughout the winter, which is part of why we advocate fertilizing, watering, and mulching your plants in preparation for the colder months.
Natural Cold Protection and Winter Growth
So what about the above-ground parts of the plant? Well, how that adapts depends on the plant in question. In some perennials, the aerial parts of the plant just die off for the winter and then re-grow in the spring. Daffodils are a fine example, as their resurgence early in the new year is a wonderful sign of spring to come. Plants that maintain their above-ground structures during the winter months have developed a variety of means to protect themselves from the cold. The most common of these involves managing the water content of their cells. By packing the cells of their above ground parts with sugars instead of water, they prevent freezing within the cells that would cause cell damage. The water moves outside the cell walls and can freeze safely and then be re-absorbed when things warm up in the spring.
Other plants get even more sophisticated and produce compounds that function as natural antifreeze. Witch hazel is a wonderful example of this sort of plant. Instead of blooming in spring or summer, the natural anti-freeze compounds this plant produces allow it to go dormant during the warmer months and then thrive in the colder weather. Witch hazel blooms in the fall and winter, even after the frost forms. It’s a remarkable plant in many ways and a reminder of how diverse biological adaptions can be. Also: these natural anti-freeze compounds are nothing like the anti-freeze in your car, so please don’t confuse the two!
Gardening All Year Long
Plants adapt to their preferred environment, and understanding those adaptations helps us better care for them. Some plants have adapted to cold using a variety of ingenious means, and that’s a good reminder that nature is wonderfully diverse and that evolution is a fascinating thing. We hope this blog both helps you understand the ways in which some plants adapt to cold, and maybe gets you interested in learning a bit more about plant chemistry and physiology. Until then, let’s continue to appreciate our gardens, both the ones that can adjust to cold weather on their owns and the ones that need a bit more care to survive the winter.
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