Freeze Damage to Plants

Doug Akers, Boone Co Extension Educator

This spring's unseasonably warm weather in late March through April 3 encouraged many trees and shrubs to leaf out earlier than normal. Newly emerged growth is quite succulent and susceptible to damage from strong winds and below freezing temperatures.  

Strong winds yesterday caused foliage and flowers of some plants to wilt.  This morning, at home and on the way to work, I saw frozen foliage and flowers of daffodils, magnolias, iris (foliage), and tree lilac (foliage).  I know there’s a lot more. And, we only had an overnight low of 29 degrees, which will likely be the “warmest” night until early next week.

With the predicted lows of around 20 degrees or colder the next few nights, emerging growth on some trees and shrubs will be damaged or destroyed.  Based on past experience, damage will be severe on Japanese maple (Acer palmatum), yellowwood (Cladrastis kentukea), hydrangeas (Hydrangea spp.), and magnolias (Magnolia spp.).  The “smart” trees are the ones stay dormant longer – the oaks, ash, birch, walnut, hickories, and evergreens.  The lush growth on many perennials will also be damaged or destroyed.   Damage will be especially severe on astilbes (Astilbe spp.), ferns, hostas (Hosta spp.), and other numerous other perennials. I spent some time getting my face wind burned late yesterday afternoon covering our two rows of strawberries, emerging hostas and some other perennials with straw.

A few people may have been timely enough with lawn seeding that new seedlings have already emerged.  I talked with Zac Reicher, Purdue Turfgrass Specialist, yesterday and he said he was more concerned about potential damage to the new grass seedlings from the wind, than the cold temperatures.  He suggested applying more straw mulch over new grass seedings, if it is in an area that the wind doesn’t just blow it off.

Symptoms
Symptoms of freeze damage include shriveling and browning or blackening of damaged tissue.  Damaged growth often becomes limp.  Eventually, damaged or destroyed leaves may drop from the tree or shrub.  

Prognosis
Fortunately, trees and shrubs have the ability to leaf out again if the initial growth is damaged or destroyed. Healthy, well established trees and shrubs should not be greatly impacted and will produce additional growth within a few weeks.  Trees and shrubs planted within the past 5 years may benefit from an application of fertilizer.  Give them some nitrogen when it warms up.  I like to apply urea (46-0-0) on trees and shrubs.  If you can’t find urea, any other high nitrogen fertilizer is just as good.  A typical lawn fertilizer, something like 23-4-8, is good.

The prognosis for freeze-damaged perennials is also good. While the freezing temperatures should damage the perennial’s foliage, their crowns and roots should not harmed.  Damaged perennials will send up new growth within a few weeks.  

Links
HO-203: Effects of Cold Weather on Horticultural Plants in Indiana

ID-168: Commercial Tree Fruit Spray Guide (pdf file)

Spring Frost Can Spoil the Show - Rosie Lerner, Purdue Consumer Horticulture Specialist

Spring Weather Gives Gardeners the Chills - Rosie Lerner, Purdue Consumer Horticulture Specialist

Gardeners-Don't Panic During Cold Weather - Rosie Lerner, Purdue Consumer Horticulture Specialist

Excellent photos of the various stages of fruit bud development and their critical temperatures:
http://www.canr.msu.edu/vanburen/crittemp.htm

Cold Weather Yellowing or Bleaching Newly Mowed Turf

KY Ornamentals April 2007 Freeze Damage

Freeze Recovery for Urban Landscapes (pdf file)

Click image to enlarge

Cold weather damage to crabapple

Cold weather damage to crabapple

Cold weather damage to crabapple

Injury to turf that was mowed (scalped) right before the cold and windy weather
Image by Doug Akers