How to Protect Plants from Frost

During the transition from summer to fall, one day may be warm and balmy while the next is crisp and clear. As a result, your outdoor plants will likely require some assistance to continue thriving during this changeover. Here’s how to protect your plants from frost.

1. Assess the situation

Before you make any plans for your plants, understand what kind of frost you might be facing. Different lengths of chill will require different actions.

If you’re preparing for a longer duration of cold, you’ll want to gradually ready your plants for the oncoming temperatures. Decrease watering so that the plants can begin to harden for the months ahead. Add a layer of compost, which will continue to feed the soil around the plant during a frost. After the first frost, replace old mulch with heavier evergreen boughs or hay—this will offer a greater level of insulation for the plant in the event of snow.

The following guidelines are for plants facing a shorter cold snap, like overnight freezes that cause hoarfrost when the dew point drops to 32ºF.

2. Create a warm environment

How you create a warm environment depends on the size and shape of the plants that need to be protected.

Ground plants

To protect plants that are low to the ground, take a blanket or sheet and drape it over the entire plant. Make sure the covering reaches the ground so it can trap heat. For added security, you can secure the cover with stakes. Cover the plant before dusk to ensure you contain as much of the day’s natural warmth as possible.

For added protection, use a layer of plastic over the blanket or sheet. However, a plastic covering should never be used alone, and any coverings you apply should be removed early the next morning. If not removed, condensation could accumulate beneath the covering, which would then lead to frost if temperatures dip again. Additionally, allowing your plants to see some sun will support them with the nutrients they need to continue thriving in cold weather.

If you don’t have a blanket or sheet, you can use a cardboard box.

1. Cut out the bottom of any cardboard box large enough to cover the plant, then tape up the flaps of one end of the box.
2. Cut along three sides of the top to create a hinged box lid.
3. Before dusk, place the box over the plant and ensure the hinged lid is closed. During the day, keep the lid open so your plant receives the sunlight it needs.

Taller plants

For taller plants, such as fruit trees, you’ll need a different approach. Essentially, you’ll create a tipi shape using burlap and stakes.

Simply drive three (or four, depending on the size of the plant) stakes into the ground at an angle around the plant. Wrap the burlap around the stakes and secure the burlap with a sturdy string or rope so that it remains closed, creating a warming fence around and over your plant.

If you think your plant could use extra warmth, fill empty plastic milk jugs with warm water and nestle these jugs around the root or trunk of the plant. This will keep the air around the root of the plant—where temperature matters most—warmer for an extended period.

Hanging plants

To best protect hanging plants from frost, bring them inside if at all possible. If this isn’t an option, place hanging plants on the ground and cover with one of the above methods, which will keep them warmer than if they had continued to hang.

How to revive plants damaged by frost

Despite your best efforts, you may wake up to discover that some of your plants have been damaged by frost. If this is the case, there are steps you can take to revive them.

1. If possible, bring the plant inside the house, placing it out of direct sunlight where it should remain for the first 48 hours, and water the plant immediately. Because frost damage occurs as a result of ice crystals wicking moisture from the leaf tissue (hoarfrost), provide your plant with a healthy amount of water.
2. Only after the plant has been inside the house for several weeks should you begin to trim dead flowers and leaves. Pruning off the dead foliage will prompt the plant to regrow.
3. Because regrowth is such an energy-taxing process, give the plant plenty of time to recover from the frost before initiating a phase of regrowth. Otherwise, the regrowth could put your plant under excessive stress, hindering its chance at survival.

If your plant cannot be brought inside to recover from frost, resist the temptation to heavily water or fertilize outdoor plants that have become frost-bitten. Offer them a normal amount of water, and then be patient and wait for new growth to occur. Once the warm weather returns, the damaged parts will likely fall off on their own.