9 Ways to Protect Your Raised Bed Vegetable Garden From Frost
Brrr! Winter is coming and so is the first frost. You still have vegetables and herbs in your raised bed garden and you want to help them through the cold spells. Fortunately, there are several tricks you can use to protect your plants from being frozen by the first frost.
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Frost can be beautiful as it sparkles in the early morning sun. It can also be deadly, killing off your vegetables before you’ve had time to harvest them. Even vegetables that are frost tolerant may not survive multiple deep winter freezes. But just because there’s cold weather headed your way doesn’t mean your crops are automatically lost.
Frost is when water vapor in the air freezes and becomes solid. You will see it on your windows, fences, and plants when the moisture that has settled on these surfaces freezes and turns into tiny ice crystals. It usually forms at night when the temperatures drop to their lowest point.
A light freeze happens when the temperature drops to 32°F (0°C), freezing, or a few degrees below. This will kill all frost-sensitive warm-weather plants but many cool-weather vegetables tolerate this amount of cold, especially with a little bit of extra protection.
A hard freeze is any temperature 28°F (-1°C) and below that lasts for at least four hours. Most garden vegetables don’t tolerate this level of freezing and will die unless protected.
You can continue to coax your raised bed garden vegetables through the first several winter frosts, and in mild winter climates, you can protect them throughout the entire cold season with a few simple materials and tricks. Check out some of these ideas to help you protect your plants from the cold and extend your gardening season.
Watch the Weather
You’ll be best prepared to protect your crops from the freeze when you know that it’s coming. First, get to know the average first frost dates for your region. As that date approaches, keep a close eye on the weather forecast.
Anytime your local weather report threatens around 35°F (1.5°C) or below, you should go into frost protection mode. 36°F (2°C) won’t kill your vegetables, but the weather forecast isn’t always right, and there are many microclimates within any given region.
A temperature of 32°F (0°C) and colder is freezing and will kill any summer crops and tender annuals, such as tomatoes, peppers, and basil. At some point, you just have to accept that these plants will succumb to winter.
Your cool-season plants will tolerate cold temperatures much better, but you’ll still want to help them along. You may find that protected spots near your house stay just slightly warmer than more exposed sites, so keep watching the weather forecast and prepare for frost anytime freezing weather threatens.
Grow Frost-Hardy Vegetables
Perhaps one of the best ways to lengthen your raised bed growing season is to grow frost-hardy vegetables. You’ll need to get your cool-weather garden bed started while the weather is still warm. Anywhere from the middle of August until early October, depending on your location and the crops you’re growing, is the ideal time to get your fall veggies in the ground.
Luckily for those who love to grow and eat vegetables, there are plenty of fall crops to choose from! By the time your summer crops are finished producing, your fall crops will be in full swing. When balancing both summer and fall crops in a small plot like a raised bed, you may have to get creative.
You can end your summer harvest a little early to plant your fall crops in time for a harvest, dedicate half your raised bed to early-season crops and the other half to late-season crops, or dedicate specific beds to different seasons and grow cover crops in between.
The following table lists examples of vegetables that are most cold-hardy, moderately frost-tolerant, and frost-sensitive crops that will die with the first freeze.
| Temp Below 28°F | Temp 28° – 32°F | Frost-sensitive |
| Brussels Sprouts | Beets | Cucumber |
| Broccoli | Carrots | Eggplant |
| Cabbage | Cauliflower | Okra |
| Collards | Chard | Peppers |
| Kale | Lettuce | Summer Squash |
| Radish | Parsley | Tomatoes |
| Spinach | Parsnips | Winter Squash |
Harvest Mature Vegetables
You’ve checked the weather and you’re expecting some freezing temperatures. Take this opportunity to harvest mature vegetables, especially those that are more sensitive to cold.
If you still have any summer crops in your garden, like tomatoes and peppers, harvest them before the first likely frost. Tomatoes frozen on the vine simply don’t look or taste good, so you may as well harvest while you still can.
Some vegetables, however, taste even better after a frost. Collards and kale are examples of vegetables that lose some of their bitterness and become sweeter after a frost. Underground roots and tubers, like turnips, carrots, and beets, also don’t need to be harvested before the frost. Wait until they are fully mature and have been sweetened by frost to enjoy their best flavor.
Water Wisely
Use water to your advantage, but you’ll need to plan ahead to use this trick best. Keep an eye on the weather forecast. A few days before any anticipated frost, water enough to make the soil moist but not fully saturated.
Moist soil actually helps hold heat, therefore keeping the soil surface warmer than the surrounding air. When you prepare and protect your raised bed garden with moist soil, the roots will be better able to survive light frosts.
Spread Mulch
Mulch is a valuable gardening tool. Spreading mulch across the surface of your raised bed garden is like giving your crops a bed with a warm and cozy comforter to protect them from frost.
Use a layer of organic material such as wheat straw, pine straw, or mulched leaf compost. You will not only be insulating your crops from the upcoming cold, but you’ll also provide a barrier against weeds, and as the mulch breaks down, it will help enhance your soil.
Spread your layer of mulch between three and six inches deep. You’ll want to cover the exposed soil but not the crops themselves. Leave a little space between your plant’s leaves and stems and the mulch.
You don’t want to smother the plants you’re trying to protect. You can safely leave the mulch in your raised bed garden throughout the winter.
Cover Individual Plants
This is a great trick to help protect smaller, individual crops from frost. Place a temporary cover over smaller individual plants to protect them from an overnight dip in temperature. It may seem like a hassle to cover, uncover, and re-cover every time there’s a threat of frigid temperatures, but this method works and keeps you active in your fall garden.
Keep a stack of large plastic pots, bins, or buckets on hand. Five-gallon buckets work great, as do large nursery pots, plastic planters, and large terra cotta pots. Do you have extra gallon-size plastic milk jugs? Cut off the bottom and place the top part over smaller plants. If you’re looking for something a bit more visually appealing, try a critter cage with a special frost cover to protect small crops from frost and critters.
You can also create your own frost covers using wire tomato cages. Place the cage around the plant and wrap the cage in a sheet, towel, or lightweight fabric cover.
Plastic bags generally don’t work as well. They are flimsy and don’t offer much insulation. A plastic bag or plastic sheet can work in a pinch but other materials are generally better for frost protection.
In the evening before anticipated frost, place a plastic covering over individual plants. Make sure the pot covers the plant completely and accommodates its full height so you don’t accidentally break or damage any taller stems. Weigh down the overturned pots or buckets with bricks if you think the wind might blow them over.
The next morning, when the air temperature has warmed again above freezing, remove the coverings so the leaves still get plenty of light. Watch the forecast every day and cover again anytime it dips to 36°F (2°C) or below. Eventually, the weather will simply be too cold, but until it is, use this easy trick to enjoy your extended gardening season.
Cover Entire Bed
When you use a raised bed garden, you can easily manage your whole garden as a single unit. Rather than covering individual plants, you can simply cover the entire bed. There are several techniques and materials you can utilize to cover your raised bed garden on demand when the temperature dips or just allow it to stay covered for the duration of the cool season.
Floating row covers are an ingenious invention and I have used them in my garden for many years. These covers are made with a lightweight fabric material that allows light and moisture to come through while offering light-duty protection from frost. As a bonus, they also protect your garden from insect pests and birds.
You’ll want to support your floating row covers with something so they aren’t resting directly on the leaves. Use metal row cover supports or build your own supports with PVC pipes, bamboo poles, or wooden stakes. Install your support system first and then drape the row cover directly over the supports and make sure it covers your entire bed.
If you’re expecting wind, hold down the edges with rocks or bricks so your cold protection doesn’t blow away. Since floating row covers allow light and moisture through, you can leave them up for a while without worrying about harming your crops.
If you don’t want to invest in a floating row cover, use what you already have on hand. Blankets, towels, or sheets make excellent frost protection helpers as well.
Drape these fabric covers over your plants the night before an expected freeze and uncover them the following morning when the temperature has warmed again to safe levels.
Use a Mini Greenhouse
A mini greenhouse may sound fancy and expensive but you can find relatively inexpensive mini greenhouses that won’t break the bank or construct your own. These structures are small, portable, and can be set up anywhere, as needed. They usually consist of a simple frame with a plastic covering and some are sized to fit perfectly over or around a small raised bed garden.
When you use a mini greenhouse, you’ll be protecting multiple plants at once. You won’t need to set up and take down your greenhouse every day, you’ll just set it up and leave it up. Most of these little greenhouses have a flap that opens to expose your plants to fresh air and rain.
Open the flap for watering and on warm days when the greenhouse might trap too much heat for your cool-weather veggies. Then, just close the flap again for cool nights to keep your plants safe and cozy.
Use a Cold Frame
A cold frame is similar to a mini greenhouse but it’s usually more box-like and typically has a hinged lid that lifts up to allow airflow and access for harvesting and watering. Cold frames are generally made of rigid materials and have wooden or metal supports holding them together. If you’re handy with tools and enjoy DIY projects, you can build your own cold frame that’s just the right size for your raised bed.
Cold frames are an excellent way to protect your plants from cold weather. Prop them open on warm days, and close them on cold nights.
Open them for easy access to your vegetables for planting, harvesting, watering, and routine maintenance tasks. When the cold season is over again, pack up your cold frame until you need it again the following fall.
Frequently Asked Questions
Oh no! My plants were damaged by the frost! Is there anything I can do?
Once frost hits your tender summer vegetables, it’s simply time to pull them out and allow winter to take over. If you aren’t quite sure if the frost has killed your plants, remove the cold damaged parts and give them a few days and see if they recover. If so, they can last a bit longer, but probably not much. If not, it’s time to let them go.
Your more hardy cold-loving plants, however, can be hit by frost and come through it just fine. Some crops, like carrots and beets, may lose their above-ground leaves, but their tasty roots growing underground are just fine! Once the tops die off, however, it’s a good time to harvest these crops.
Keep watering your beds to keep the soil moist (not wet), and don’t fertilize your plants during the winter; even if your plants look ragged, fertilizer won’t help them recover from frost. For your more frost-hardy plants, just keep offering them some protection and they will keep growing and producing.
Can I protect my plants through the whole winter?
Depending on where you live, you can maintain a winter garden, even through the worst of the winter weather. In the most severe winter climates, growing vegetables outdoors in January and February may simply be impossible. In mild and moderate winter climates, however, using greenhouses and cold frames allows gardeners to produce crops non-stop.
What should I do with my frost-damaged plants?
If your hardy plants just experienced a light frost, even if they look slightly damaged, there’s a good chance they’ll recover if you just allow them to keep growing in place. Once your plants have succumbed to frost and have turned black and soft, you can remove them entirely from your garden.
If your plant material showed any signs of pests or diseases, it’s best to dispose of these parts so they can’t spread to healthy plants. Any plants that appeared healthy before being killed by frost can be composted.
What should I do with my raised bed for the rest of the winter?
After removing all the winter-killed vegetables from your raised bed garden, you may be wondering what to do next. Pull out any weeds you see, especially before they set seed and populate your garden with another generation of weeds. You can also take advantage of the winter season to get some garden tasks done.
If the soil level in your raised bed has fallen during the growing season, replenish with fresh soil so your garden is ready to go in the spring. You can also add mulch to your raised bed, if you haven’t already, to help protect and nourish the soil.
