On cool nights in spring and fall, there is often the risk of frost. If you live in a warmer climate, you may see frost during the winter. The plants that we love to grow, such as beans, tomatoes, petunias, and others, will not survive a night of freezing temperatures. Can you protect your plants from frost by using a tarp?
Yes, you can use a tarp to cover up your plants during a frost, but there are some better methods. Instead of a tarp, use something more breathable, like a cotton sheet or pillowcase. You can even purchase a frost blanket, which is lightweight and durable.
The answer really depends on how long and how cold the frosty weather will last. If it’s a night or two of frost, with a rebound to warmer temperatures over the coming weeks, it does make sense to use a tarp to protect your plants if that’s all you have.
You just need to take a few common-sense precautions to ensure that your plants emerge from the tarp in good enough condition to keep pumping out blooms and fruit.
Table of Contents
- How to Use a Tarp to Protect Your Plants from a Frost?
- Should You Use a Tarp to Cover Your Plants from Frost?
- What Can Happen if You Cover Your Plants with a Tarp?
- Can You Cover Your Trees with a Tarp to Protect them from Frost?
- What are Some Better Frost Protecting Alternatives?
- At What Temperature Should You Cover Your Plants?
- How do You Know a Frost is Even Coming?
- What Happens if You Don’t Cover Up Your Plants?
- Will One Night of Frost Kill my Plants?
- Final Thoughts
How to Use a Tarp to Protect Your Plants from a Frost?
If you are using a tarp to protect your plants, try to set it up before the sun goes down.
You will want to capture the warmth from the sun-warmed soil under the tarp, so you need to cover things up before the heat starts to dissipate as the evening cools off.
It’s also recommended that you keep the soil moist, as it will hold more heat than dry ground.
You should keep the tarp from actually touching the plants, if at all possible. Not only can the weight of the tarp damage them, but cold can be transmitted through the plastic to the foliage.
This is a lot easier when covering small plants in spring. You can set empty flowerpots or plastic containers over the individual plants before laying the tarp down over top of them all. This not only gives an extra layer of insulation against the cold, but also prevents the seedlings from getting crushed by the weight of the tarp.
In fall, your tomato and pepper plants will be strong enough not to be crushed, but fruit or foliage that is right up against the tarp may get nipped by the frost. Try using wooden stakes to hold the tarp away from the plants if at all possible. Don’t use metal stakes, as they will conduct the cold right down to the plants.
Always secure the edges of the tarp to prevent it from blowing away and exposing your plants to the cold. Bricks, stones, or lumber can be used to anchor down the edges, and you should clip the ends together to keep the cold air from getting in.
Should You Use a Tarp to Cover Your Plants from Frost?
Using a tarp to protect your plants from frost is really only a short-term solution to cold temperatures. You have to remove it first thing in the morning to let the sunshine reach the plants.
Unless you see warmer weather in the forecast, it’s best to start to clear out the tender plants rather than try to stave off the inevitable.
Still, when there’s a chance of frost, and you feel there’s lots of life left in your garden, grabbing a handy tarp from the garage can be a great way to extend the harvest.
Of course, at the beginning of the growing season, you will want to keep your summer crop safe, so it’s certainly better to use a tarp than nothing at all.
What Can Happen if You Cover Your Plants with a Tarp?
There are some potential problems to using a tarp to protect your plants from frost.
Plastic tarps are what most people have available, and plastic can easily transmit the cold, especially if there is moisture trapped underneath as well.
As well, if you don’t get out early to remove the tarp the following morning the plants can be damaged by high temperatures and humidity when the sun starts to beat down on the plastic cover.
A heavy cotton tarp will provide better protection, but can easily crush delicate plants.
Can You Cover Your Trees with a Tarp to Protect them from Frost?
Using a tarp to protect your trees from frost can be a difficult job, especially once your trees grow larger.
Frost is only really a danger to trees that are blossoming in spring, when a late frost can destroy an apple or peach crop, or a show of flowers on a magnolia.
It can be very challenging to get a large enough tarp to cover your tree. As well, securing it properly over the tree so that it doesn’t blow away may not be possible.
However, if you have a small tree and can rig up a heating source under the canopy, you may have success with using a tarp.
On the whole, though, it’s best to try different methods to protect your spring-blooming tree from frost.
Luckily, there are better ways to protect your plants and trees from frost that don’t involve using a tarp.
Even a cotton sheet or pillowcases can provide protection from a light frost. An old comforter is even better. Just make sure that the fabric is not touching the plants, if possible.
Another form of protection that can work well with spring seedlings is a cloche. You can make your own by cutting the bottom off of plastic jugs. That way, you divert plastic waste from the recycling bin as well as protecting your plants.
If there’s frost in the forecast, you can set your sprinkler to run overnight. This can protect your plants from severe damage, even if ice forms on them.
Many commercial orchards and vineyards use frost fans to keep the air circulating on frosty nights in spring. If your garden is compact enough, you could set up a large box fan to maintain a good airflow when frost is likely.
Frost blankets are an excellent commercial solution to the cold snap. Widely available from garden retailers, the spun polypropylene fabric can be supported on hoops to cover crops for several weeks, as water and sunlight will pass right through.
You can even get polypropylene frost covers to zip over small fruit trees.
At What Temperature Should You Cover Your Plants?
While water freezes at 32°F (0°C), it’s best to cover up tender plants when the forecast calls for overnight temperatures of 41°F (5°C). When it comes to frost, it’s better to be safe than sorry!
Depending on the topography of your garden, you could get frost in one spot and not in another. Cold air settles, so low spots are most at risk. However, if you have the time and materials, covering anything that you don’t want to get hit is the best approach.
How do You Know a Frost is Even Coming?
When you are a gardener, the weather forecast is your friend.
Especially in the shoulder seasons in spring and fall, keep an eye on the daily forecast so you will know what to expect.
You can also purchase a home weather station which may include a frost alarm, letting you know when the temperatures have fallen into the danger zone.
For long-term planning, it’s a good idea to acquaint yourself with the usual first and last frost dates for your location. Often your best resource will be other local gardeners or farmers, but you can also find that information easily online.
What Happens if You Don’t Cover Up Your Plants?
The answer to this question depends on the specific plants, and how hard a frost it was.
For instance, a mild frost might only hit in certain sections of your garden, especially if you have lower spots where the cold air settled.
As well, even tender plants may be saved if you get outside early enough before the sun starts thawing things out.
Pouring or spraying water over foliage that has been affected by a light frost may save them. You may also find that covering them up with a sheet or blanket will slow down the rate at which the cells thaw, preventing them from rupturing.
However, a severe fall frost will generally damage any tender annuals or perennials so that they won’t survive. If the stems are mushy and the leaves are limp and black, it’s time to clean things out for the winter.
It’s important to understand that not all plants are susceptible to frost, so even if you are covering up parts of your garden, focus on those plants that will not survive a freeze.
Will One Night of Frost Kill my Plants?
Not all plants are going to be killed by even a hard frost late in the season. Cold-hardy vegetables such as broccoli, brussels sprouts, and carrots can bounce back and keep growing.
Flowers such as petunias and impatiens will be killed by frost, but chrysanthemums, flowering kale, and sedum will continue through to a hard freeze.
In spring, vegetables such as lettuces, peas, and onions will not suffer from a frosty night, while tender tropical natives such as tomatoes and peppers will die unless protected.
Spring flowers such as tulips, daffodils, and primroses are unaffected by frost.
Gardeners are always trying to push the boundaries of what they can grow in their climate zone. After all, what would a summer garden be without tomatoes, beans, squash, and peppers, all tropical plants that will be killed by frost?
Even the most careful gardener who plants according to first and last frost dates may be caught off guard by a freeze in June or September. Knowing how to protect your plants when frost hits can extend your growing season by weeks. A tarp is one of the ways that you can keep your garden safe.
Janice is a retired High School teacher who is spending her leisure years keeping busy with all sorts of projects. Aside from freelance writing, she’s an enthusiastic amateur chef, home wine maker, and tends a large raised-bed vegetable garden, while at the same time running a Bed & Breakfast.