How to Keep Plants Warm Long After Summer Ends

Your grandma may have used this trick when an early freeze threatened her garden because it’s free and easy to do. Just try to keep the material from touching the plants (tall plant stakes help with this). Note that if the fabric is too porous, it can allow moisture to penetrate and freeze your plants anyhow. But if it’s all you have on hand, give it a go. Make sure to remove them in the morning once the sun is up.

Have a few short plants that you want to protect from freezing? Turn an empty pot upside down to cover them for the night. Remove in the morning. It’s a DIY variation on a cloche or a hot cap, which have been used for centuries in Europe to protect individual plants.

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There’s actually some science behind this one—and it’s a totally free option! By clustering pots together and placing them up against your house, they’ll benefit from the heat that accumulates during the day. The heat that radiates off the exterior of your home offers protection by creating a slightly warmer microclimate for your plants. Obviously, you can only do this with containers or potted plants. Covering the pots with blankets adds another layer of insulation.

According to Goff: “We know that row covers are very effective and can raise the temperature from 2 to 8 degrees for the plants underneath them.” That’s not a ton, but it can be enough to prevent the plant from freezing, especially if you use a cover that’s designed to protect within a certain temperature range. Some row covers, also called frost blankets, provide protection down to 20 degrees Fahrenheit. Check the label carefully before you check out.

This is a technique that farmers use, so we know it works. “It doesn’t have to be fancy or a commercially bought item to be effective,” says Goff. Simply create a hoop shape by sticking a thick gauge wire or bendable metal stake into the ground to create an arch. Then, drape the plastic or row covers over top, securing them with landscape pins or rocks. Note: Prefab PVC tunnels also are available.

If you’re a hardcore gardener who is serious about frost protection, a mini greenhouse may be the answer. While they can be expensive, there are more affordable plastic options that will suffice if you’re just trying to get a few extra weeks out of your plants.

A cold frame is a bottomless box with a clear glass or plastic top that lets sunlight in and allows for ventilation on warm days. They provide more protection than other methods, but the plants can overheat on sunny days, so you’ll have to monitor the temperatures. In most parts of the country, you can plant crops that don’t mind cooler weather, such as lettuce and spinach, directly in a cold frame in late summer for a harvest through early winter. They’re also great for getting a head start on your spring garden because the ground inside a cold frame warms up faster.

It’s not always possible, but you may be able to save some of your plants for next year by bringing them indoors—or at least into the garage overnight. Small potted plants may do fine when placed in a sunny south- or east-facing window, but others may require supplemental lighting such as an LED grow light, which can be standalone or attached to a shelving unit. Plants that are typically good candidates for overwintering include annual herbs, such as basil, and perennial herbs, such as rosemary and thyme, says Goff.

You may have less success with overwintering ornamental plants, but give it a shot if you’ve got the space and can’t bear to part with a particularly gorgeous begonia or a stunning succulent that’s not cold-hardy. In addition, some flowers can be saved for planting again next year by digging up their tubers, bulbs or corms in cold climates. For example, dig up dahlia, gladiolus, elephant ear and caladium bulbs after a frost, brush off the excess dirt, then store them in a cool, dry place over the winter. Plant them in the spring after all danger of frost has passed (and crossing fingers, they will blossom once more).