Issue 1, April 24, 2018

Protecting Plants and Trees from Frost Damage

Illinois weather has a great ability to change at a moment notice. Because of this, our plants have to acclimate or they will not survive.   The last couple of weeks have been no exception. As far as I can see, we have many plants in bloom as well as trying to leaf out.  The plant is the most susceptible to frost damage with all this new growth. However, a temperature of 30 degrees overnight probably will not seriously impact plant health. We usually don't start seeing significant damage until the temperature gets down to 28 degrees or lower. In addition, some of the heat captured during the warm daytime temperatures radiates back, and helps to protect our plants overnight.

I wouldn't recommend trying to cover daffodils, tulips, or other bulbs. Any sheets or mulch we use will probably crush the flower stalks we're trying to protect. Flowering shrubs like azaleas and lilacs should probably be covered with sheets or light blankets during the colder nights.  Strawberries should be covered with straw or a sheet to protect the blooms. Be sure to remove the mulch and sheets during the day. Do not use plastic sheets or tarps: they don't have any insulation to them, and any plant parts that touch the plastic will get frost damaged.

When cool weather strikes our trees in the spring they do suffer and can affect each slightly differently. Young succulent growth can be killed causing shoots and leaves to be discolored, twisted, or distorted.  The injury symptoms can look very similar to herbicide injury. The affected leaves, buds or flowers eventually drop.  A saving grace for trees and shrubs is that they possess secondary and tertiary buds to allow for regrowth.   This does cause the plant to dip into their stored reserves and could cause them to be more susceptible to additional injury throughout the growing season.    

Taking care of trees, ornamentals and flowers is a matter of understanding how they grow naturally and using that understanding when we take care of them by properly watering, fertilizing, mulching and pruning.   Time will tell if the plant will survive or recover from the frost injury.   Be sure to wait before you jump into prune out suspected dead sections. Special care needs to be given to those plants that have sustained injury so that they do not go through additional stress in the growing season making them vulnerable to diseases and insects. So look at your plants this week and prepare them for this crazy weather we are having and hopefully they will continue to look good throughout the year. (Maria Turner)

Maria Turner

Return to table of contents