Extension News

Ask the ISU Extension Garden Experts About Winter Damage to Trees and Shrubs

tree and shrub winter care


Snow covered shrubs and small trees

How do I prevent damage to small trees and shrubs from heavy, wet snow?

The weight of heavy, wet snow can cause considerable damage to small trees and shrubs. In late fall, multi-stemmed evergreens, such as arborvitae, can be wrapped with twine or rope to prevent damage from heavy snows. When heavy, wet snow accumulates on small trees and shrubs gently shake the snow from their branches or carefully brush off the snow with a broom. When cleaning driveways and sidewalks, do not throw heavy, wet snow onto small trees or shrubs. Also, avoid dumping snow onto small trees and shrubs when raking snow off roofs. 

Protection from cold temperatures

Can anything be done to protect trees and shrubs from cold winter temperatures? 

It might be possible to protect marginally hardy, small shrubs by encircling the shrubs with chicken wire fencing and filling the enclosure with straw or pine needles. In most cases, however, little can be done to protect trees and shrubs from cold winter temperatures. 

Iowa is located in USDA Hardiness Zones 4 and 5. The average annual minimum temperature in Zone 5 is -10 to -20 degrees Fahrenheit. The average annual minimum temperature in Zone 4 is -20 to -30 degrees Farhenheit. The dividing line between Zones 4 and 5 lies roughly from Council Bluffs to Ames to Dubuque. 

The best way to prevent damage caused by low winter temperatures is to select trees and shrubs that are reliably winter hardy in your area. 

Check out the ISU Extension publication Deciduous Shrubs to learn more about selection and care of shrubs. Publications are available from the Extension Online Store at www.extension.iastate.edu/store/.

Snow on evergreens

I have several small evergreens in my yard. Do I need to uncover the evergreens if they get buried in snow? 

No, there is no need to uncover the evergreens. The snow will not suffocate the evergreens. The snow acts like an insulating blanket and protects the evergreens from desiccating winter winds.

Deicing salt damage

How can I prevent damage to trees and shrubs from deicing salts? 

Homeowners can minimize salt damage by using deicing salts prudently. Before applying salt, wait until the precipitation has ended and remove as much of the ice and snow as possible. Use deicing salts at rates sufficient to loosen ice and snow from driveways and sidewalks, then remove the loosened ice and snow with a shovel (deicing salts need to be applied at much higher rates to completely melt ice and snow). Mix salt with sand or another abrasive material. Fifty pounds of sand mixed with one pound of salt works effectively.

Avoid piling salt-laden snow and ice around trees and shrubs. While the amount of salt applied to major roadways cannot be controlled, steps can be taken to minimize damage. As soon as the ground thaws in early spring, water areas where salt accumulates over winter. A thorough soaking should help flush the salt from the root zone of plants. If possible, alter the drainage pattern so winter run-off drains away from ornamental plants. When planting trees near major streets or highways, select salt-tolerant tree species.

Guidelines for Selecting Trees, RG 0702, a Reiman Gardens publication, can be downloaded from the Extension Online Store. To ask the ISU Extension garden experts questions, call the Hortline at 515- 294-3108, Monday-Friday from 10 a.m. to noon and 1 to 4:30 p.m., or e-mail us at hortline@iastate.edu.

Contacts :

Richard Jauron, Horticulture, 515-294-1871, rjauron@iastate.edu

Willy Klein, Extension Communications and External Relations, 515-294-0662, wklein@iastate.edu

December winter scene (photo download). The 2010 Extension garden calendar features this photograph. Beautiful photography as well as gardening and wellness tips fill the 2011 garden calendar available from the ISU Extension Online Store at www.extension.iastate.edu/store/.