Take steps to protect trees from harsh winter weather
Q: What can I do to protect my trees and shrubs from frost damage, in case we have another "polar vortex" winter?
A: You are wise to think about protecting trees and shrubs from winter's brutal winds and freezing temperatures. While you can't prevent damage in every situation, you can take steps to help trees and shrubs on your property handle winter stress.
Winter damage to plants occurs due to exposure to temperature fluctuations such as a warmer than average autumn, cold early winter and then another warming before another drop. This stresses a plant's ability to know when to break dormancy. Most trees and shrubs that are hardy to average weather conditions for our area can handle temperature fluctuations within our USDA Zone 5 range. The sudden extreme cold that a polar vortex brings can shock, damage and even kill a plant that is not hardy in our temperature zone and can challenge one in a vulnerable site exposed to wind or salt spray. Here are some steps to prepare your trees and shrubs for winter.
• Plant evergreens and trees in August or September, but no later, to allow them time to get hardened-off or prepared for winter. Newly planted trees and shrubs whose root systems are not yet well established also need to be watered with 2 inches per week if no rain or snow occurs up until the ground freezes.
• Avoid late summer/autumn fertilization and pruning to established trees and shrubs. You do not want new growth at this time. New growth now will not harden-off before winter. Water your established shrubs and trees up to 1 inch per week in lieu of rain or snow up to the ground freezing. Shrubs, especially evergreens, and trees need to be watered well before winter as once the ground freezes they will go dormant.
• Mulch 2-3 inches around trees to the drip line and around shrubs once the ground freezes so roots are protected from the frost heaves that occur from freezing and thawing. Roots cannot survive freezing temperatures below the area lows in your zone so you need to keep them warm and in place with mulch.
• Be aware that "volcano mulch," where the mulch is piled up high on a tree trunk, makes it easy for insects to infest a tree, and for rodents and other small animals to eat bark, which can kill a tree. "Donut" mulching around the trunk to be able to see the trunk flare at the bottom is the correct way to mulch. For shrubs exposed to wind and/or salt spray, you can erect a barrier built of burlap or canvas fixed to stakes as tall as your shrubs. This can protect them from the winter burn that causes brown areas in evergreen shrubs come spring.
If you follow these steps you are more likely to see less damage from winter stress and polar vortexes.
- Nancy Degnan
• Provided through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.