10 Easy Ways to Protect Plants from Frost
Simple tips for protecting your garden from killing frost
One day it's 65 and sunny. The next, it's 32 with snow on the ground. Yep, that's spring—a magical time of year filled with burgeoning life and fluctuating thermometers.
For many of us, spring presents one of the year's greatest gardening challenges: protecting tender new growth from damage due to cold. Frost damage, freezing death, root damage and frost cracks on bark are four primary negative effects of severe drops in the temperature.
Monitor the weather so that you can prepare for frost.
How do you protect plants from frost?
In early spring, when the threat of frost is especially great, closely monitoring weather conditions via weather radio, TV, and/or websites for reports of expected cold spells is imperative. That way, when frost is predicted, you can prepare for it.
Here are 10 easy, practical methods I've used to reduce frost's impact on my garden. One or more of them might easily work for you, too.
10 Easy Ways to Protect Plants from Frost
Cover plants before nightfall.
Make sure plant covers extend down to the soil.
Covers don’t have to be elaborate or expensive in order to work. A row of sticks with newspaper, cardboard or sheets and towels tented over them will do just fine.
If you don’t have sticks, lay the covers directly over your plants. This too will prevent heat loss.
If you’re going to cover up your plants before a hard frost, do so before dusk. If you wait until darkness falls, most of the stored heat in your garden will have dissipated.
No matter what type of cover you use, make sure that it extends down to the soil on each side. In the morning, after the frost has thawed, remove the covers.
Good for garden rows or raised beds, a large fabric plant cover will protect tender spring flowers & vegetables from cold en masse, and it can be used year after year.
Warm plants with water jugs.
Fill plastic milk jugs with water and place them in the sun, allowing them to soak up heat during the day. Before dusk, set the jugs around your plants and throw a cover over them. The water in the jugs will lose heat more slowly than the soil and the air, and the warmth it emits will keep your plants warm.
Water before a frost.
It may sound crazy, but watering around plants the night before a spring frost can actually protect them from freezing. During the night, the wet soil will release moisture into the air, which will raise the temperature and keep plants warmer.
When not in use as protective covers outdoors, glass cloches make stylish covers for indoor plants.
Cover plants with cloches.
Strictly speaking, cloches are removable glass or plastic covers that protect plants from cold. Sometimes called bells or bell jars, most fit over individual plants, but some are large enough to cover a row.
Glass cloches are highly ornamental. When you're not using them outside for frost protection, you can use them indoors over humidity-loving houseplants like violets.
Stake lightweight cloches into the ground to prevent them from blowing over.
Plastic cloches are generally less expensive than glass ones. Because they are lightweight, they must be staked into the ground to prevent them from blowing away in high winds.
Like other covers, cloches should be placed over plants before the sun goes down and removed in the morning after the frost has thawed.
12 Ways to Repurpose Milk Jugs in the Garden (Including as Cloches)
Place plants in frost-resistant spots.
It's as true for plants as it is for real estate: location, location, location. Set out seedlings and store-bought spring plants in areas that are less likely to experience damaging cold.
U.S. Frost & Freeze Maps
The last frost date in the spring and the first frost date in the fall indicate how long your growing season will be. You need to know these dates so that you can determine when to start seeds indoors, and when to purchase and plant nursery plants.
For freeze/frost dates in the U.S., visit the National Oceanic and Atmospheric Administration (NOAA). Freeze-date tables, as well as other frost/freeze information, are also available through your local state cooperative extension office. Click here to find the site of an office near you.
As cold air moves to lower ground, it will pass by plants located on high ground or slopes. That's why it's best to place seedlings and other plants that are susceptible to frost in these locations. Shrubbery also provides protection from light frosts.
Placing plants by walls and fences can provide additional protection, particularly if the structures are dark in color. During the day, the structures absorb heat. Throughout the night, they radiate it, keeping plants warmer than they'd otherwise be.
Avoid frost pockets.
Frost pockets are depressions in the ground. Cold air drains into these "pockets," and it can't get out. When this happens, plants located in the depressed areas can suffer frost damage. Avoid sowing seeds and bedding new plants in these low places.
Harden off seedlings.
Before setting out seedlings, acclimate them to the outdoors by gradually exposing them to conditions outside. This process, called hardening off, will help you grow stronger plants that are more likely to withstand the vicissitudes of early spring.
Begin the hardening off process about 14 days before transplanting. When the weather's mild and above 45 degrees F, place the seedlings outside during the day in a warm, shady spot that's protected from the wind. At night, bring them indoors.
After two weeks, the seedlings will be stronger, sturdier plants, ready for transplanting.
Place hanging baskets on the ground before covering them.
Place hanging baskets on the ground, and then cover them. They'll absorb some of the ground's warmth and be less likely to sustain frost damage.
Protect potted plants.
When frost is predicted, bring planters and hanging baskets inside.
The roots of potted plants experience more severe temperature fluctuations than those planted in the ground. They'll reach lower temperatures, too. That's why potted plants are especially susceptible to root damage due to cold. It can cause their roots, particularly those near the edge of the pot, to turn spongy and black. Although root damage may not kill the plant, it will stunt its growth.
If you opt to cover a hanging basket rather than bring it inside, place it on the ground first, and then place the cover over it in order to take advantage of the ground's relative warmth.
Wrap fruit trees.
If you grow fruit trees, be sure to wrap the trunks in the fall with burlap strips or tree wrap. Most fruit trees have thin barks that are susceptible to splitting when temperatures fluctuate dramatically. will prevent this splitting, which is known as frost crack. Tree wrap
Choose cold-hardy plants.
Some vegetables and flowers are hardy souls that thrive in spite of (or sometimes because of) the cold. Crocuses often push their way through snow to bloom, and a spring storm rarely gives narcissus, tulips, grape hyacinths, or pansies pause.
Like pansies, calendula (also called pot geranium) is an edible flower that's frost resistant. Other cold-hardy edibles include broccoli, cabbage, carrots, chives, leeks, lettuce, peas, radish, spinach, and Swiss chard.
Experts at your local nursery are great sources of information about hardy plants appropriate to your zone. Most likely, native plants, particularly native perennials, will be the best choices.
About the Author
The Dirt Farmer has been an active gardener for over 30 years.
She first began gardening as a child alongside her grandfather on her parents' farm.
Today, The Dirt Farmer gardens at home, volunteers at community gardens and continues to learn about gardening through the MD Master Gardener program.
© 2011 Jill Spencer