Dirt on Gardening

I field a lot of questions from anxious gardeners in the early spring when the temperatures are fluctuating. They are concerned about frosts and freezes, and the damage these may do to the tender green plant shoots coming up in their flower beds.

A covering of frost is not uncommon in the Ozarks throughout the early spring months. In the Ozarks, the “average date of last frost” is different depending upon each zone, but is usually between April 10 and May 10.

A frost is when the water vapor in the air condenses and freezes. The temperature must be at 32 degrees Fahrenheit or lower for this to occur. Tender plants such as annual vegetables and flowers like tomatoes and impatiens will be killed by a simple frost. However, hardy annuals like lettuce and spinach will not be harmed by a frost.

In most cases, the daffodils and other bulbs, shrubs like forsythia and lilac and perennials like peonies and poppies will not be harmed by a frost each evening. These plants are specifically hardy to the cold temperatures of a frost. A freeze may damage these plants.

A freeze is when the surface temperature is at 32 degrees Fahrenheit or less. Most damaging to plants is a hard freeze – when the surface temperature is at 25 degrees Fahrenheit or less for a day or more. Sustained freezing temperatures from a hard freeze will kill buds on trees and plants that would not ordinarily be affected by cold temperatures that go away when the sun rises and warms the earth.

The terms “frost advisory” and “freeze warning” have been developed to warn gardeners of the risks their plants have outdoors when the temperatures are dropping into that 32 degree or less range during the day or night.

Occasionally, we have severe freezes in the spring that ruin the blossoms on early blooming plants and shrubs, but usually mother nature maintains an almost miraculous balance between cold and warm temperatures allowing a little new green growth each day but not too much to cause plants to prematurely sprout and bloom.

In general, gardeners should be very cautious about placing annuals outside in the early spring. One frost will zap an annual, and these plants do not like the colder evenings anyway. It’s best to wait to place annuals outside when the danger of frost has passed.

Blankets, sheets or towels can be applied to tender perennials that are budding when a freeze is to occur overnight. Do not use plastic as a covering; moisture will develop under the plastic that can freeze and damage the plants.

Should a hard freeze occur in the next few weeks, there’s very little a gardener can do other than keep his or her fingers crossed that some blossoms will survive the extreme temperatures.

Questions or comments related to gardening? Contact Joleen at missourigardener@hotmail.com

Leave a comment

Leave a Reply