7 Ways to Protect Garden Plants From Frost: Covers, Mulch, and More

Last Updated on October 18, 2024

Don’t let the cold stop you from gardening, or kill your precious plants! Come learn several easy and inexpensive ways to protect your garden plants from frost. All it takes is a little creativity and preparation.

This post will cover seven effective garden frost protection methods and tips, including the use of garden bed covers, cloches, mulch, careful selection of plant varieties, watering and more. We’ll also explore frequently asked questions about what kinds of plants need frost protection (or not) and at what temperatures.

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How Frost Damages (or Benefits) Plants

When plants are exposed to freezing temperatures and frost (which can occur at 36°F or below), ice crystals form and burst plant cells – most commonly within their leaves. When this happens, it disrupts the plants ability to provide water or nutrients to those areas. In turn, frost-damaged leaves or plant tissues appear soggy, scorched, dark, thin, and limp. Young and tender plants are the most susceptible to frost damage, so they will need more protection during a cold snap. 

Keep in mind that even if they look sad, many plants can bounce back from mild frost damage! Frost usually impacts fresh new growth and the outer perimeter leaves the most, but that doesn’t mean the plant roots are dead or won’t continue to grow. Plus, many cold-tolerant perennial plants and trees go dormant during the winter time. They shed their leaves and hunker down for the winter, rebounding with fresh green growth come spring.

Some plants even benefit from extended periods of cold. For instance, many fruit trees require a certain number of “chill hours” to properly develop fruit. Kale and other members of the brassica family become increasingly sweet in flavor after a kiss of frost!

Which plants should I protect from frost? Hardy versus tender plants

Frost doesn’t impact all plants equally. Plants are characterized by the degree of cold temperatures they can tolerate, classified as either “hardy” or “tender”. 

Tender plants have soft, succulent tissues and are easily damaged or killed by freezing temperatures (unless protected). Examples of tender plants include summer garden crops like tomatoes, basil, cucumber, squash, peppers, and eggplant along with tropical fruit trees (citrus, mango, banana, avocados), succulents, most annual flowers, and common houseplants. Young sprouts and seedlings are also considered tender, even if they’ll grow up to be cold-tolerant plants (such as broccoli or cabbage seedlings). 

On the other hand, hardy plants can withstand frost or short-term freezing conditions. Hardy annual vegetable plants include common cool season crops like cabbage, broccoli, kale, cauliflower, Swiss chard, carrots, radishes, turnips, and beets. Once established, these types of plants should readily survive a light frost or even temperatures in the high 20s with little-to-no protection.

Some cool season crops are more on the tender side, like lettuce, mustards, and bok choy. These leafy greens do enjoy cooler conditions but their thin leaves will become more easily damaged when exposed to frost (without protection) than tougher, thick-leaf hardy vegetables.  

Preparing Your Garden for Frost

In addition to physically covering garden beds and plants to protect them during a frost or freeze warning (which we’ll cover next), there are a number of easy ways to proactively prepare your garden plants for frost too.

• Choose season-appropriate plants. Meaning, grow heat-loving plants in the summer time and cold hardy plants in the early spring, fall, or winter garden. This may sound like common sense, but could confuse new gardeners! For instance, even though it’s called “winter squash”, hard squash and pumpkins should be grown during the summer; they’re not frost tolerant.
  
  
• Select varieties thoughtfully. Certain varieties of kale, spinach, or cabbage may be more frost-tolerant than others. If you have harsh winters, selecting the most hardy varieties will help the plants survive longer! Different plant cultivars also have varying days to maturity, which is important to consider if you have an especially short growing season. Choosing faster-maturing options can help maximize your harvest before the deep freeze sets in.
  
  
• Harden off seedlings. If you start seeds indoors like we do, be sure to harden off seedlings by gradually introducing them to outdoor conditions before transplanting them outside. All seedlings are fairly frost-sensitive, but especially those that haven’t been properly acclimated first.
  
  
• Have an action plan. Keep an eye on your weather forecast, and have a plan in place (including necessary supplies on-hand) to respond to frost and freeze warnings. Be ready to harvest any remaining frost-sensitive fruit, or cover crops as needed. Many northern gardeners leave hoops on their garden beds year-round, making it easy to throw frost cloth over in a jiffy.

At what low overnight temperature should I cover my plants?

It depends on the hardiness and age of plant.

According to the National Weather Service, frost advisories are usually issued when overnight temperatures are forecasted to be between 33 and 36°F. During a frost warning, plan to cover young seedlings, tropical plants, summer garden crops, and other tender (cold-sensitive) plants. Just to be safe, I’d consider protecting those types of plants with a forecast of 40 or below since the weather forecast isn’t always accurate!

Freeze warnings are issued when temperatures below 32°F are forecasted, and when significant and widespread freezing is expected. Cover, move, or otherwise protect tender plants during hard freeze warnings. Even hardy and mature winter garden crops will appreciate added protection when temperatures dip below freezing, especially for an extended period of time. When in doubt, cover them!

Frost and freezing is also more likely to occur in rural areas or open microclimates that are less sheltered by buildings, roads, and trees. We learned that lesson the hard way when we moved to “the country” and started seeing significantly more frost than at our old urban homestead, even with similar overnight lows predicted!

How to Protect Plants from Frost

Now let’s explore 7 effective ways to protect your garden from frost, including hoops and frost cloth, plastic poly tunnels, cloches, cold frames, sheltered planting locations, mulch, and watering practices. I’ve included a few tips for protecting potted plants from frost too!

1) Cover Garden Beds with Frost Cloth, Blankets or Fabric

One of the best ways to protect plants from freezing conditions is with specialized frost cloth or fabric garden bed covers, also known as horticultural fleece.

Perched over vulnerable plants (usually supported by hoops) frost cloth offers added insulation and shields against the icy moist air. In fact, garden frost covers can protect plants from frost damage even in outdoor temperatures as low as 20 degrees – depending on the type of frost cloth used! Garden fabric warms the soil, which protects roots and also helps spring-planted seedlings grow better during otherwise chilly conditions.

Garden frost covers are available in various shapes, sizes, and temperature ratings. See the chart below. Here where it rarely gets below 30F, we use a fairly lightweight frost cloth (.55 oz). Colder climate gardeners would want to choose something thicker, such as this 1.2 oz cloth or this heavy-duty 1.5 oz frost cloth. We usulaly buy large sheets/rolls and then cut it to fit over individual garden beds. Some frost covers even come in a dome-shape, ready to cover shrubs or small trees.

In a pinch, something as simple as an old bed sheet, blanket, drop cloth, roll of burlap, or sleeping bag can help protect plants from frost damage too. 

2) Use Plastic or Poly Tunnels

Sheets of thick plastic (like greenhouse plastic, or even a tarp) can be used in a similar manner as fabric row covers to protect plants from frost and snow. When supported on a series of arched hoops, they’re referred to as polytunnels.

One benefit of polytunnels is that they don’t block sunlight (assuming clear plastic is used), so they don’t need to be completely removed for the plants to photosynthesize like thicker frost cloth. However, plastic isn’t nearly as breathable as fabric garden frost covers, so it’s important to open the ends of the tunnels during the daytime to give plants some much-needed airflow.

3) Cover Individual Plants with Cloches

Cloches are ideal for protecting a handful of individual small plants from frost, rather than covering an entire garden bed or area. Cloches are dome-shaped (often made of clear plastic) and sit over plants to act like a mini greenhouse. You can purchase cloches or turn average buckets, food storage containers, cut milk jugs, 2-gallon soda bottles, or other random materials into homemade ones!

4) Grow in a Cold Frame

Cold frames are small structures that cover plants or garden beds, designed to protect them from freezing conditions. Similar to a mini greenhouse, cold frames made of transparent materials such as clear plastic or glass that allows sunlight in. They are constructed fairly low to the ground and close to the plants. Create a simple DIY cold frame by laying old windows or frames of plastic over a raised garden bed. 

5) Protected Locations

Careful site selection for frost-sensitive plants will make both of your lives easier! Tender plants will be significantly more happy in a protected location. Plus, you’ll save time, energy and stress by not having to fuss over them so much. Therefore, it’s best to avoid planting tender perennial plants in open spaces where they’re fully exposed to cold air and wind. 

You can find or create a microclimates within any yard space! For example, plant less hardy trees and shrubs near a west or south-facing wall or structure to provide valuable radiant heat and create a space that is several degrees warmer than nearby open areas. It will also help to block chilly gusts of wind. Large shrubs, fences, boulders, and canopy cover from trees offer similar protection for nearby plants.

For example, we recently planted a row of pineapple guava and loquats (both hardy below 20F) that will grow into a large living wall and help shelter the nearby sensitive avocado trees from cold wind.

Protecting potted plants in winter

To protect potted plants from frost, move them to a more sheltered location such as indoors, against the house or under eaves, to a covered porch or greenhouse, or even under the shelter of a large tree. Clustering many potted plants together also helps. Mobility is a definite perk when it comes to winterizing potted plants!

On the other hand, potted plants are more susceptible to frost damage because their roots aren’t as insulated as those planted in the ground. Thus, in addition to adding frost cover on top, you may want to wrap the pots of especially sensitive plants (or, on freakishly cold nights) with a blanket, horticultural fleece, or even bubble wrap for added protection. Also, don’t forget the mulch!

6) Mulch

Cover bare soil! Mulch adds a protective layer that insulates soil, buffers again temperature swings, holds in warmth, and can prevent the ground (and roots) from freezing. This goes for potted plants too! A few excellent mulch options include compost, small bark, wood chips, straw, and chopped leaves or leaf mold. Read more about the pros and cons of 8 popular types of garden mulch here. 

Applying a nice deep layer of organic mulch around the base of shrubs, young trees, evergreens, or tender perennials will help protect the plants from frost damage. Aim for about 2 to 4 inches deep. You could even cover low-lying plants completely with a layer of fluffy mulch (such as straw) for a short period of time.

7) Water Before a Frost

It may sound a little counter-intuitive, but watering your garden before an exceptionally chilly evening can help protect plants from frost damage. Stressed, thirsty plants are more susceptible to frost damage. Also, damp soil provides superior insulation, holds in heat, and freezes less deeply than dry soil.

When frost is looming, water earlier during the day. This gives the plants ample time to absorb water and get perky for the cool evening ahead. Keep in mind that damp soil is good, but overly soggy soil could actually make the problem worse. That also goes for any time in the garden! 

Take care to water the soil only and not intentionally wet the plant’s leaves. One frost prevention trick used in the agricultural industry is to directly spray plant foliage with water. However, that method is most effective when the water is continually sprayed throughout the period of freezing (such as overnight via overhead sprinklers in an orchard or vineyard) – not as a single application of water before a frost. When the spraying ceases, the water droplets left on the plant leaves will freeze. 

And that sums up this list of ways to protect your garden during frost.

All in all, many plants are more resilient than we think. Even tender veggie plants may recover from leaf scorch, wilt and browning caused by frost. Just give them some time. I hope this article gave you a few new ideas to extend your growing season! Did I miss any clever ways you protect your plants from frost? Let me know in the comments below, and feel free to ask questions as well.

To dive even deeper into the world of winter gardening, I highly suggest the book “The Year Round Vegetable Gardener” by Niki Jabbour. If you found value in this article, please spread the love by sharing it. As always, thank you for tuning in!

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