When you see a cold snap looming in your forecast, you need to act fast to protect plants from dangerous temperatures. Fortunately, you have lots of options for frost protection even if you’re not prepared in advance.
Frost damage occurs when the air on the surface of your plants is cooled to freezing temperatures, and the water in the cells forms ice crystals.
When water freezes it expands, and this causes the cell walls to burst. Plants damaged by frost will show slimy wilted foliage, burned growing tips, or a completely dead plant.
Because hot air rises, covering your plants with one of the following methods will trap the warm air around your plants so that temperatures stay a few degrees above those outside.
Not all plants are as susceptible to damage from frost. Some plants can protect themselves from a light frost by increasing the sugar content within their cells.
The increased sugar lowers the freezing point of the water in the cells just enough to protect the cell walls from damage, and these plants will actually taste better if they are grown through a frost!
If your first frost is a few weeks away, then you still have time to build a low tunnel or cold frame.
However, sometimes frost warnings pop up unexpectedly, and you might not be ready with a low tunnel or cold frame. If that’s your situation, don’t worry! I have some quick solutions for frost protection that you can use in a pinch.
The first two suggestions for protecting plants from frost not only offer frost protection but actually create a microclimate that will significantly extend your growing season.
Use a low tunnel to protect plants from frost.
A low tunnel is a short greenhouse tunnel placed over your plants. They are usually only 2-4 feet tall.
You create a low tunnel by placing what we call hoops every few feet and covering the entire bed or row with plastic or agricultural fabric. The covering works by trapping warm air under the tunnel to raise the temperature a few degrees which protects your plants from frost overnight.
This method using fiberglass rods is the easiest and fastest way to make hoops that I’ve seen!
For the cover that you’ll place over the hoops, you may choose a lightweight fabric like garden fleece or Reemay which will protect plants from frost down to about 28 degrees Fahrenheit. If it’s colder than that, you’ll need to use a thick UV resistant plastic sheeting.
Don’t forget to place rocks or bricks around the edges to hold the fabric or plastic down, and make sure that at least one side of your tunnel can be lifted for harvesting.
During periods of warm days and cool nights, you may need to open the ends of the low tunnel during the day to let out some heat. This is especially true if you decide to go with plastic sheeting.
Low tunnels are one of the best ways to grow more food during colder months. They can be customized to fit the length and width of your garden bed and are easily stored when not in use.
Build a cold frame for frost protection.
A cold frame is basically a small greenhouse that can be placed over your a garden bed.
Cold frames can be built with scrap lumber and old windows like this one from This Old House.
However, it doesn’t need to be that complicated. It can be as simple as setting some hay bales around your plants and placing a window on top.
A cold frame provides excellent insulation and protection from wind and cold weather. However, while there are many uses for cold frames, this type of frost protection does limit your growing space. And, depending on the construction, the walls can block some of the light that your plants receive.
For these reasons, a cold frame is most appropriately used for small garden beds.
Use a cloche to cover your plants in winter.
A cloche is a tiny greenhouse house you place over individual plants. This is a great option if you have just a few seedlings or small plants in the garden that need protection.
They are usually made of plastic or glass and may be rigid or flexible like these popup types. You can also make your own from 2-liter plastic bottles or a milk jug.
But what if frost is in the forecast and you don’t have a cold frame or low tunnel ready?
You have several options to protect your plants from frost even if you didn’t plan ahead.
Basically, you can cover them with anything you have on hand. For individual plants, grab a bucket, flowerpot, or even a cardboard box to put over them for the night.
If your plants are sturdy, you can lay garden fleece, burlap sack, blanket, tarp, or sheet right on top of the garden bed.
If your plants are small and fragile enough that laying a blanket right on top of them could break the stems, then use stakes or blocks to provide some support underneath your cover.
Be aware, though, that thinner covers like bed sheets may not provide complete protection and the tips of plants can still get bit by the frost where the cover touches them.
In any case, you absolutely must remember to pull the cover off in the morning or you might smother your plants.
If you can’t find anything to cover your plants, consider leaving a sprinkler running overnight.
That sounds crazy, right? I thought so when I first heard it!
But keeping your plants wet can actually protect them from freezing. Make sure you read about using sprinklers to protect plants from freezing before deciding to use this method.
So if you find yourself facing a frost, don’t give up hope on your garden!
Using one of these techniques you can keep your plants protected and growing healthy food even into the winter.
Have another idea for protecting your plants from frost? Leave me a comment below!