How To Protect Plants From Frost

November 21, 2022

Frost can be life-threatening to outdoor plants, especially less-hardy plants like tender bulbs, tropical plants, and summer annuals. When temperatures dip below 28 degrees (a hard freeze), the water inside the plants can freeze, resulting in dehydration and possible death.

These five tips can help you reduce the likelihood of plant frost damage.

1. Place tender plants in frost-resistant areas

Cold air falls and heat rises, so if you have seedlings or tender annuals in small pots, place them on a bench or picnic table overnight to keep them away from ground-level freezing air. (These plants will not survive the cold air that pools in low-lying areas.) You can also place tender, semi-hardy plants close to buildings, especially next to dark-colored walls that face south and west. These exteriors absorb more heat during the day, and radiate warmth at night.

2. Cover your plants before sunset

Covering your plants insulates them, trapping heat radiating from the soil to keep them warm overnight. Basic household items are perfect for preventing plant frost damage — milk jugs, empty plant pots, buckets, sheets, and drop cloths.

Remember to remove the coverings in the morning. Otherwise, condensation will build up under the insulator and do exactly what you’ve been trying to avoid: freeze your plants.

3. Keep plants warm with jugs of water

Because water is denser than air, it takes longer to cool down. So, if you’re expecting a hard frost, fill milk jugs with hot water and place them under your plants’ coverings for the night. The heat that the jugs release will help keep your plants warm enough to survive until the sun rises.

4. Properly water your plants before a frost

Keeping your plants well-watered during winter is another great way to help prevent
plant frost damage — overwatering them can cause root damage or freeze their leaves. It’s also best to water in the evening. Moist air tends to be warmer than dry air, so humidity rising from the ground will keep your plants warmer through the night.

Additionally, wet soil absorbs more of the sun’s heat during the day. Because moist soil often remains warmer than dry soil, this can keep your plants from freezing as temperatures dip.

5. Bring potted plants indoors

If you are anticipating a frost, bring potted plants inside for the night. It may seem easier to cover them, but roots have less protection in pots because there isn’t enough soil to keep them insulated. Because of this, potted plants are at a greater risk of freezing when temperatures drop, even if they’re covered.

However, be sure to keep them separate from your indoor plants to avoid transmitting disease. Better yet, if you have a garage or a shed that stays warm overnight, store your outdoor potted plants there.

Plant frost damage is a major worry for gardeners during winter nights. But if you implement these five tips, you’ll be much more likely to keep your plants safe until sunrise.