Kelly Jackson
Christian County Extension Office
Fall Frost Damage to Plants
Freeze damage to woody plants in the fall is just like plant damage in the spring, in that the newest growth (also termed softwood growth) will receive the most substantial damage. Also, broadleaf evergreens seem to bear the brunt of damage compared to conifers or deciduous trees and shrubs.
Most of this new softwood growth occurs in early-mid fall (September until the freeze date) and is the result of improved environmental conditions in the fall (lower temperatures and more soil moisture). This “fall flush” of growth is encouraged by high fertility levels and abundant soil moisture and for these reasons, generally it is not recommended that fertilizer be applied in the last third of the growing season, unless you are trying to correct a nutrient deficiency. It’s also recommended to taper off irrigation, especially to established shrubs and trees, during fall.
Freeze damage occurs to this softwood growth when temps drop below 32F and gets progressively worse below 25F. This fall, summer drought was followed by abundant rainfall and good growing conditions (temperatures in the upper 60sF) which encouraged a flush of new growth. Then an unexpected drop in temperatures to 16F occurred November 11 to 13 before the new growth had the chance to harden off for winter.
At this point, new growth will die back completely to the point where the fall growth was initiated. Symptoms are similar to spring freeze damage in that stems and foliage will wilt and turn a dark brown/black to purple color. The only real remedy for this is to tip prune damaged stems or wait for spring bud break, which will cover damaged growth with time. Some flowering shrubs and trees may be less showy next spring. The full extent of damage will not be realized until new growth starts next year.
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UNIVERSITY OF KENTUCKY, KENTUCKY STATE UNIVERSITY, U.S. DEPARTMENT OF AGRICULTURE, AND KENTUCKY COUNTIES, COOPERATING