How to Keep Plants Warm Long After Summer Ends
Although it may be hot and steamy now, summer won’t last forever. And if you’re deep into the gardening trend like millions of others, you know how you feel about your plant babies: You love them so much, and it’s tough to say goodbye to them at the end of the season! Luckily, you can extend the growing season by protecting your plants from unexpected cold snaps or early frosts. There’s just one tiny caveat: “Some plants aren’t suited for cooler weather,” says Jen Goff, associate product manager of tools and supplies at Johnny’s Selected Seeds. “Warm weather crops such as tomatoes, peppers and eggplant respond not only to temperatures, but to light. Once the days start to shorten, their growth and vigor also decreases.”
That doesn’t mean you can’t try to eke out a few extra weeks from your garden anyhow. If you hear that an early frost or a hard freeze is coming (apps such as Accuweather are helpful for this), there are steps you can take to provide some insulation, which may save your plants for a little longer. Many of these tips aren’t scientifically proven—and there’s always risk when nature is involved—but it’s certainly worth experimenting, which is how you keep learning, says Goff. And trust us: There’s always something new to learn about gardening!
Here are a few ways you can keep plants warm:
1. Cover them in old sheets or blankets
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.
2. Shelter them using overturned pots or cloches
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.
3. Use the heat from the house
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.
4. Try row covers
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.
5. Make your own hoop tunnels
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.
6. Invest in a mini greenhouse
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.
7. Get a cold frame
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.
8. Overwinter your plants
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).