(Click on smaller image to view larger image.)
|Spring freeze injury on birdsnest spruce
(Photos by Karen Rane)
|Spring freeze injury on maple
(Photos by Greg Bossaer, White County CES)
|Spring freeze injury on maple
(Photo by Peggy Sellers)
On the night of April 17, 2001, temperatures dipped below 32 degrees Fahrenheit in Indiana, causing light damage to plants across the state. We also had freeze damage the morning of April 26th, and had one last freeze, mostly in the northern quarter of Indiana on May 13th. Symptoms from these low temperatures are still apparent on some plants. Late spring freeze injury is a type of cold injury that results from low temperatures in late spring or when a plant has broken dormancy too early. Cold temperatures damage young tissue as leaves are emerging from their buds. Many species of plants may be affected by freeze injury including trees, shrubs, flowers and vegetable plants. Depending on the plant and the severity of the frost, the plant will often recover.
Symptoms of a late spring frost often appear as brown, black, curled, and shriveled leaves and stems on new plant growth. Affected leaves often are tattered as they continue to expand, especially on oaks and maples. This tattered appearance often resembles insect feeding damage.
New succulent growth of young herbaceous plants and evergreens can be very susceptible to frost. Leaves of herbaceous plants may turn black and stem tips may curl after a freeze. New growth on evergreens, such as spruce and yew, often turn brown and curl in response to freeze injury.
Maples and other broad-leaved trees often develop a tattered or puckered appearance. Often small pockets of leaf cells on developing leaves are killed by frost. As the leaf matures, these pockets do not grow and become holes that appear more prominent as the leaf reaches mature size. Sometimes these pockets of cells are simply damaged and continue to grow at a slower rate than the rest of the leaf, creating a ruffled, distorted shape.
Although symptoms from freeze injury can look alarming, most plants will grow out of the injury. Most herbaceous plants will drop any dead leaves on their own. Pruning freeze injured tissue will improve the appearance of the plant. However, do not be too quick to prune out growth as many plants will put out new buds just below the point of dieback.
Minor injury to leaves of broad-leaved trees should not affect the tree's overall health. If the freeze injury is severe, the plant may drop the damaged leaves, replacing them with new ones. If severe freeze injury occurs during consecutive years, the tree's health could be affected.
Spring freeze injury of some plants can be prevented at the time of planting. When possible, choose a site that allows cold air to flow away from it, such as the side of a hill. If this is not possible, choose a site where the plant will not be fooled by sunshine into breaking dormancy too early. Planting on the north and east sides of the house will delay bud break. Choosing plants that flower and leaf out later in the spring is also an option for preventing spring freeze injury.
Freeze injury may also be reduced by covering perennials and small shrubs with leaves or evergreen branches in the fall. Mulch beds in mid-November to prevent smothering of the plants. Covering herbaceous plants will keep them from coming out of dormancy too early in the spring, thereby avoiding freeze injury. If a freeze is predicted, another method of prevention is to cover small shrubs and herbaceous plants with blankets, tarps, or other material to provide insulation from the drop in temperature.
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Last updated: 25 June 2001/tlm.
The Plant & Pest Diagnostic Laboratory at Purdue University.