AMES, Iowa – This spring's unseasonably warm weather in late March and the first three weeks in April 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.
Then along cam freezing temperatures in late April and early May in Iowa to damage or destroy the emerging growth on some trees and shrubs. Damage appears to most severe on Japanese maple (Acer palmatum), northern catalpa (Catalpa speciosa), hackberry (Celtis occidentalis), katsuratree (Cercidiphyllum japonicum), yellowwood (Cladrastis kentukea), smokebush (Cotinus spp.) ginkgo (Ginkgo biloba), hydrangeas (Hydrangea spp.), magnolias (Magnolia spp.), oaks (Quercus spp.), and black locust (Robinia pseudoacacia).
On the other hand, most maples (Acer spp.), birches (Betula spp.), green ash (Fraxinus pennsylvanica), honeylocust (Gleditsia triacanthos), lilacs (Syringa spp.), lindens (Tilia spp.), and viburnums (Viburnum spp.) seemed to have suffered little or no damage.
The unseasonably warm weather in early spring also encouraged lush growth on many perennials. The freezing temperatures in recent days also damaged some perennials. Damage has been noted on astilbes (Astilbe spp.), bergenia or pig squeak (Bergenia spp.), ferns, hostas (Hosta spp.), and other perennials.
The extent of plant damage is dependent on several factors. These factors include temperature, plant species, exposure, and stage of plant growth.
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.
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 3 to 5 years may benefit from a light application of fertilizer and periodic watering during dry weather.
The prognosis for freeze-damaged perennials is also good. While the freezing temperatures damaged the perennial’s foliage, their crowns and roots were not harmed. Damaged perennials will send up new growth within a few weeks.