Frost is simply frozen condensation. It occurs at temperatures below freezing, i.e. 32F and 0C.
HOW DO YOU PROTECT PLANTS FROM FROST?
Essentially, you just need to cover your plant with some kind of material to trap warm air around your plants so that temperatures stay a few degrees above those outside the cover. You can throw almost anything over your plants as long as it doesn’t squish them and you take it off in the morning.
CONSIDER PLANTING FROST RESISTANT PLANTS
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!
WAYS TO PROTECT PLANTS FROM FREEZING TEMPERATURES
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.
A LOW TUNNEL
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 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.
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
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.
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 PLANT CLOCHE
A cloche is a tiny greenhouse 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.
All cloches should have some venting so that they don’t cook the plants the next day. Otherwise, make sure you’re out there as early as possible to remove the cloche before the sun comes up.
DIDN'T PLAN AHEAD? YOU HAVE SEVERAL QUICK OPTIONS TO PROTECT YOUR PLANTS.
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.
Remember to pull the cover off in the morning or you might smother your plants.
DON'T HAVE A COVER? LEAVE A SPRINKLER RUNNING OVERNIGHT
Keeping your plants wet can actually protect them from freezing. Be sure to read this first before trying a sprinkler.
Pest and Disease Help
University of Maine Cooperative Extension- Pest Management