How to Protect Plants from Frost

Using garden covers like frost cloth and floating row covers is an excellent way to protect your plants from frost, sleet, snow, and cold winds. Covers allow you to grow further into the fall or winter and start earlier in the late winter or spring. This extension of your growing seasons includes adding an extra layer of protection for cool-season seedlings moved out to the garden in the early spring. Depending on your climate, the right frost protection can even allow you to grow all winter long.

Here's something to keep in mind: Unless you opt for more advanced protection like a greenhouse or cold frame, covers can only protect your plants down to about 24°F or so. Once your temperatures dip below that (what we call a deep freeze), most of the plants in your kitchen garden will either go dormant if they have good root structures or die off. For cold-hardy perennials, frost protection can help them bounce back a bit quicker in the spring.

We're also not really talking about protecting warm-season plants like tomatoes. You might be able to buy yourself another week or two for your tomato plant to finish ripening its fruits, but it's better for your garden's overall health to remove frost-sensitive plants like cucumbers and tomatoes when you see an upcoming frost in the weather forecast.

Let's look at four different levels of protecting your cool- and cold-season plants from frost.

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DIY Frost Protection for Plants

Level one of protecting plants from frost is ideal for those occasional cold snaps where the temperature dips below 32 degrees Fahrenheit overnight. Basically, if you live in a warmer climate and don't experience frost very often, you might not need to purchase any special products to protect your garden from frost.

Instead, just grab some old towels, sheets, and even bedspreads. Fabric is great to trap warmth radiating from the ground and from the soil. Fabric covers also prevent any moisture in or on your plants from coming into direct contact with freezing air.

If you're gardening in containers, consider bringing them inside temporarily. Otherwise, you'll need to cover each container well and tuck the cover underneath the container to ensure no cold air can get inside. Another option is to turn a plastic tub upside down and place it over your container plants. Make sure to place something heavy on top (like a brick or hand weight) so the tub doesn't blow away and leave your plants stranded in the cold.

The key to using DIY frost protection is to use materials that fully cover your garden space and reach the ground. Again, the idea is to create a warmer microclimate under the cover to trap heat from the ground.

These covers don't allow for sunlight to reach your plants, so they should be removed as soon as temperatures rise above freezing. If you're expecting more frost the next night, it's a good idea to still remove your covers for a bit to give the sun time to warm the soil again. This also releases any moisture that was trapped underneath the cover.

Frost Cloth for Plants

Frost cloth and frost blankets are similar to using old sheets and towels in that you're trapping warmth from the soil underneath the fabric. But these products actually let in a bit of air and sun. How much air and sunlight varies from product to product. Some frost cloth is tissue-thin to allow plants to breath. AG 30 frost cloth provides about 6°F of protection (meaning if the air temperature is 30°F, the air underneath the frost cloth will be about 36°F) and allows about 70 percent of sunlight through. This is a great medium-weight cover to consider.

Frost cloth, also called garden fleece, is a great option for you if you've just planted seeds or seedlings that need frost protection or if you want to extend your growing season for perennial herbs and frost-tolerant plants like Swiss chard, beets, kale, spinach, carrots, lettuce, and cabbage.

Frost cloth is light, easy to install, and easy to store in between periods of wintry weather.

Tips to Use Frost Cloth

• Most frost cloth arrives in a big roll, so it's easy to cut more than you need and then double it by folding it in half for more protection.
• Stretch garden hoops across your garden to support the frost cloth so that your plants don't come into direct contact with cold cloth.
• Tuck in your plants like you would a child at bedtime—snugger than a bug in a rug! Air pockets around the edge of the frost cloth can let outside air in, which can lead to frost damage on your plants. Tuck in every corner, even the back of your garden (this can sometimes be a challenge if your raised garden beds are up against a fence or structure).
• Use landscaping pins or garden staples to push through edges of frost cloth to hold it in place. If your raised bed has a top trim like the Gardenary-style raised bed, you can also use clamps or greenhouse clips to secure your frost cloth around the edges of the trim. Weight frost cloth down using rocks or bricks in hard-to-reach places, like the back of your raised garden.

Frost Cloth Options on Amazon

Here are some reusable frost cloth recommendations to make your life easier:

• Lonurya Frost Cloth for Raised Beds (includes one 8ft x 24ft white cover that can be cut down to fit your space, plus 8 landscape pins and plastic gaskets to hold cover in place)
• WYRJXYB Blanket Plant Covers (includes 10ft x 30ft white frost cloth, 6 garden hoops, and 12 plastic clips)
• The Planket (includes 10ft x 20ft dark green cover)
• Remiawy Plant Cover (includes 8ft x 24ft white cover)
• Agfabric Floating Row Cover (includes 5ft x 25ft 1.2oz heavyweight white cover)
• Agfabric Floating Row Cover (includes 5ft x 50ft 0.55oz white cover)
• De Witt N-Sulate Plant Protection (10ft x 12ft 1.5oz white cover)
• Flarmor Floating Row Cover (10ft x 50ft 0.55oz white cover)

Row Covers and Hoop Houses to Protect Plants from Frost

Now we're going to take it up a notch and provide even more protection for your vegetable garden with heavy-duty plastic draped over the frost cloth. Farmers often use what they call low tunnels to protect their crops, and we can take that concept and use it in our raised garden beds. Unlike frost cloth, plastic sheeting does not let water or air in, but it does let in a varying amount of sunlight, depending on the thickness of the plastic.

Level three allows you to grow cold-tolerant veggies like carrots and spinach during periods of cold weather, but know that these crops will likely slow down their growth. I've seen gardeners in very cold parts of the country use these plastic tents to keep their plants alive in the winter, not necessarily thriving and growing, but alive.

This plastic sheet allows snow to slide off easily instead of accumulating, and it also adds 5 to 15 degrees more protection than just frost cloth alone. The hoops are important for structure because we don't want the plastic to touch our plants at all. (Plastic can trap moisture on the plant and contribute to frost damage.) You'll want to remove at least this plastic layer as soon as the temperatures rise so that your plants can get some fresh air.

Tips to Use Plastic Sheeting as Frost Protection

• To protect your plants on this level, you'll first need to install garden hoops or PVC pipes to each end of your raised garden bed and then every couple of feet in the middle, depending on how long your bed is. Your goal is to slide the hoops or pipes deep into the soil of your raised beds and then create a nice, tall arch over your plants.
• You'll then cover your hoops with frost cloth and secure it in place.
• Finally, you'll cover your hoops with plastic sheeting and secure it in place.

Cold Frames and Mini Greenhouses

Short of having a large greenhouse, the best protection you can offer your plants is with a semi-permanent structure like a cold frame or mini greenhouse. This level is best for those of you with a true cold season. That means you have months where your average temperature doesn't reach above 32°F and there's always a chance for frost or snow.

A cold frame is a 5-sided structure with sides and roof made of glass or plastic. The structure is placed on the trim around a raised bed or directly on the soil around crops, and the angled roof of the cold frame should face South in order to capture as much sunlight as possible. The plants inside a cold frame will obviously still receive sunlight and enjoy temperatures about 10°F warmer than the outside air. (Keep in mind that factors like the level of humidity inside the frame and the amount of sunlight it receives can impact the temperature.)

Another option for protecting individual plants from frost and snow would be garden cloches, which are basically bell-shaped mini greenhouses.

Cover Your Kitchen Garden This Spring and Fall to Extend Your Growing Seasons

No matter which level of frost protection you use, covering your garden will level up your garden game.

Don't forget to water your garden the day before a freeze is expected since wet soil releases heat more slowly into the surrounding air. You could also add mulch or organic compost around the base of your plants before temperatures drop below freezing to help trap the soil's heat.

Thanks for being here and making gardening ordinary, even when wintry weather is headed your way!