By Erin Marissa Russell
When the first frost of the year is on the horizon, many gardeners begin to wonder how to keep their plants alive during the winter. There’s no need to say goodbye to all the plants you’ve worked so hard to nurture this season—not with the wide variety of methods that are available to help your plants flourish all year long. Keep reading to learn the steps to take when temperatures drop so your plants make it through the winter so you can enjoy them next year, too.
Do plants die if they freeze?
Long story short, whether a plant will die in freezing temperatures depends on the plant and the climate where it comes from. Plants that are native to the tropics, for example, aren’t likely to survive once temperatures dip below freezing. On the other hand, there are some plants that are hardier in cold weather and can make it through a freezing winter without any help from the gardener.
We’re all familiar with what freezing temperatures do to water: the liquid water is solidified into ice. This process occurs within plants as well, changing the water inside the plant into ice crystals. The jagged edges of these tiny bits of ice gash and shred the cell walls inside the leaves and stems, causing cold damage and even complete loss of your prized plants.
Learn more about winter hardy vegetables.
What is the lowest temperature a plant can survive?
In short, most plants will see serious damage after what’s termed a “killing freeze,” which is when temperatures fall to 28 degrees Fahrenheit or lower. That’s in contrast to a freeze in terms of the weather, when temperatures are officially considered freezing once they drop under 32 degrees Fahrenheit. A killing freeze will damage the top growth of most of the garden: perennials and root crops. (Not sure whether your plants are annuals or perennials? Check out this Gardening Channel article on the difference between annuals and perennials.) What it takes to cause cold damage can differ widely from plant to plant due to a broad range of factors.
For example, some plants are just cut out to withstand colder weather than others, and some can handle a quick drop in temperatures better than longer stretches of cold. Additionally, some parts of your garden offer more protection from the cold than others (like when a house or shed blocks some plants from the wind or casts a chilly shadow over some of the yard). So plants in more protected parts of the garden will fare better than those that are more exposed to the elements.
Tropical plants can suffer from cold damage after a very short spell in temperatures under 32 degrees Fahrenheit—as in just a few hours. On the other hand, hardier specimens such as shrubs and trees can stand strong throughout the chilliest winters without suffering any damage, bouncing back to lush, green growth the following spring. Plants that can withstand long cold spells have this capability because they’re built to weather the winter, using mechanisms like dormancy or the waxy coating on evergreen needles to make it through the freeze.
How do I protect my plants from freezing?
When you need a short-term way to see plants safely through an unexpected cold snap or winter storm, there are several ways to protect them from freezing temperatures. Gardeners can be proactive by making sure to use a generous layer of mulch in the garden, which helps to keep the soil warmer when the weather turns chilly. As an alternative to mulch, add a layer of wood chips or straw six to eight inches deep.
One method for protecting plants in a freeze is simply to cover them with a floating row cover (or the DIY version, a large tablecloth or bedsheet). Plants standing on their own can be capped with a flowerpot turned upside down or an upturned bucket. Protect roses by raking a mound of soil around them 12 to 18 inches tall, which can keep the crown safe from freezing. Make sure to remove these protective elements once the sun comes out and things warm up so your plants can start to warm up, too—and so they don’t go too long without the sunlight they need to thrive.
Before a cold snap comes through, you should water plants deeply. Not only will you know they’re adequately hydrated during the freeze: wet soil can actually help your plants make it through the chilly temperatures. When soil is damp, it retains the heat better than dry soil. That means recently watered plants are more likely to stay warm than plants that weren’t watered before the freeze came through.
Of course, there’s always the option of bringing plants that are in pots indoors for a while to weather the storm. If you find that you need to move plants frequently, you may choose to store the heaviest containers on dollies so they’re simple to move without straining your back—simply roll them from one place to another.
These short-term strategies for handling cold weather can be counted on to protect plants when temperatures drop a few degrees below what they can normally withstand, and only for short periods of time. In cases when the weather will fall more than a few degrees under a plant’s hardiness threshold or when cold will last for an extended duration, you’ll need to use more long-term solutions.
Want to learn more about protecting plants for the winter?
Chicago Tribune covers Freeze Versus Frost: How Cold Affects Plants
Gardening Know How covers Protecting Winter Plants