The evergreen trees and shrubs throughout Casper were severely damaged on November 9-13, 2014 when the temperature dropped from 60 degrees to 27 degrees below zero. The evergreens were not entirely dormant due to the warm temperatures when this weather event occurred, thereby causing the needles to freeze and die. You may have noticed these dead needles when you saw that some of the evergreens around the city are a reddish brown color. Some evergreens were not affected by this weather event because they were completely dormant due to freezing temperatures previously in October that signaled the evergreens to move toward dormancy. Evergreen dormancy is a genetic determinate that varies from species to species. All evergreens do not go dormant at the same time. It had been so warm up through November 9, 2014 that many trees were not ready for the extreme cold weather, and this is the reason that the needles are now dead.
The damaged evergreen trees are NOT necessarily dead. We will need to wait and see if the tips of the damaged branches (the terminal buds) are dead. If the tips (terminal buds) come out green, then the evergreens will grow out of this damage. The reddish/brown needles will most likely fall off, and the tree will look a little bare for the season, but eventually the terminal bud will grow new needles. Watch for new growth from the terminal bud as we move into May, and then prune off the branches that don’t grow green needles from the terminal bud.
If your evergreens are not dead and begin growing again this season, then there are some extra precautions that you will need to put in place to ensure their healthy recovery. First, you will need to provide adequate water and fertilizer to compensate for the loss of energy producing needles. Second, due to the extreme stress caused by this freeze damage, the trees will be susceptible to disease and insects. Stressed trees will likely need arborist applied treatments to ensure that they remain healthy during recovery. Third, you will need to be patient while these trees don’t look good for a few years as they re-grow new needles.
Spring will reveal some additional freeze damage to our deciduous trees (trees with leaves) and perennials. You may notice dead tips throughout Cottonwood, Elm, Ash, Linden, and Birch trees. You may notice more significant die-back on ornamental trees, fruit trees, and shrubs that are not native to this zone. It has been a difficult time for all of our trees with the limb breaking storm of October 2013 and now the needle freezing storm of November 2014. Many trees, shrubs, and perennials will need a little extra care and pruning to help them overcome this freeze damage. A little care, patience, and persistence will encourage the beautiful trees of our city to thrive again.