Frost Warning

It’s getting to that time of year when we have frost warnings. Last night and the night before were such cases. We have learned through hard lessons to err on the side of caution when it comes to a frost.
Frost occur when the temperature falls below freezing, usually at night. The frost is sometimes evident in the early morning light as a white “frosty” covering on the grass and other vegetation. This is not to be confused with a hard freeze. A hard freeze will cause damage to plants left anywhere outside, even of covered.

Tender plants such as impatiens, geraniums, and tropicals like the elephants ears, Boston ferns and vegetables like tomatoes and peppers are susceptible to frost damage. The freezing air causes leaf damage as the cells rupture when frozen. If you have ever left a can of soda in the refrigerator you will know what happens. The liquid expands when frozen and with the case of plants the cell membrane is damage and the cell dies.

Since the annual plants get their energy from the leaves the plants die.
Perennial plants, on the other hand store their energy in the roots so they may die off this year, they will come back next year. Perennial plants do not need to be covered.

Plants in containers can be moved to a spot where they will be under cover such as a porch or under an awning. Other plants such as those in large containers or planted directly in the ground need to be covered up where they are.

Materials used to cover the plants include newspaper, plastic, plastic bags, sheets or other material that can be loosely laid over the plants. If the wind is blowing its a good idea to use a covering that can be tied down but since many frosts occur on still nights this usually is not necessary.

The plants will probably need to be uncovered in the morning as the sun on plastic can cause the temperature to spike causing damage from heat. It’s a delicate balance between a quick frost and temperatures in the 80 or better but that is one of the challenges with growing in zone 4.