Why does a frost or freeze hurt plants and what can you do?
A widespread frost, and a freeze for some, is likely Friday night into Saturday morning. A freeze occurs when the temperature drops below 32 degrees, and frost can happen when the air temperature (which is measured about six feet above the ground) is up to about 36 degrees. If part of your yard is lower than the rest, it’ll probably be coldest there since cold air is heavier and sinks down.
Frost is the coating of ice crystals that forms on the outside of plants. Hardy plants are usually not affected much by this, but sensitive ones can be. For a freeze – in particular, a “hard freeze” of 28 degrees or colder – the damage is greater.
Plant cells have water in them. When that water freezes, it expands and the ice breaks through the walls of the cells. The parts of a plant that have soft tissue, such as leaves or new shoots, are most affected. And the colder it is, or the longer the cold temperature lasts, the higher the chance of the stronger tissues also being harmed.
If you can’t bring your plants inside, there are a few ways you can protect your plants from the upcoming cold snap:
- Put them against a south or west-facing wall, since that will get the most warmth in the afternoon and evening and radiate some of that warmth back out at night. Being under an overhang may also help.
- Give the soil around them a good soaking. Wet soil holds warmth better.
- Cover them with a light sheet that can breathe. Remove the sheet in the morning once the temperature starts rising.