Unexpected spring and fall frosts strike panic in the hearts of many gardeners. There's no
way we can accurately predict or control the temperature, but there are several measures to
protect plants from these light frosts.
First, plan for frosts. Contact your local weather bureau to find out the average first fall
frost and last spring frost for your area. In St. Louis, these dates are October 15 and April 15
respectively. These dates will help you judge planting and harvesting dates so you can plan for
frost protection. Remember, these are only averages. Actual dates can fluctuate widely.
Before you plant, check your site. Since cold air sinks, low areas freeze earlier in the fall
and later in the spring. Areas close to lakes usually have later fall frost dates. Plants sheltered by
buildings or larger plants are often missed by first and last frost of the season. The heat from
buildings, cities and artificial sources also affect frost dates. You may want to record the
temperature in your own yard and compare with the average for the area. This will help you
decide whether or not to protect your plants from frost when warnings are out.
Here are some guidelines. Protect plants from a light frost (down to 28 degrees F) by
covering the plants with cloth, plastic, newspaper, straw or evergreen boughs before the frost
occurs. Boxes and inverted pails can also be used. This will help trap soil heat around the plants
and prevent the cold air from striking them. Remove the coverings, especially plastic, when the
temperature rises above freezing.
A commercial practice that some gardeners may like to experiment with is to use water to
protect plants from frost. Lightly sprinkle tender crops with one eighth inch of water per hour.
As the water freezes on the plant, it gives off heat which keeps the plant from freezing. You
must continue to sprinkling until the ice melts off the plants which makes this technique less
practical. Do not use this method on trees, shrubs or other plants that could be broken or
damaged by the weight of the ice on the plants.
See ways of protecting plants from frost