To clear up any potential confusion in this article I’ll be talking about the genus Cedrus. The most common varieties being “Blue Atlas,” “Lebanon,” and “Deodar.” These are really amazing trees that add unique color and structure to any landscape, and because they are an evergreen they contribute year round. They are generally listed as a USDA hardiness zone 6 to 9. The Boise area is listed as a 6 on the USDA hardiness map when we have winters like this though we are probably closer to a 5. This puts the Cedar into what is commonly referred to as “borderline hardy,” so most years it will be just fine. This, unfortunately, was not most years.
Cedar Tree Freezing
A few years ago, the Boise area witnessed a unique weather event in which temperatures dropped almost 40 degrees in a single evening. This drastic change in temperature came without warning and many trees suffered greatly because of it. The full effects from this weather event would not be fully realized until the following spring. Cedars were one of the affected trees, and this winter has been just as hard on them. With the temperatures beginning to rise you may have already noticed some symptoms of this freezing damage.
Symptoms of Freezing Damage
By the time your trees show any symptoms of freezing damage, it has been almost a month since the damage occurred. Because it takes so long to show up, it will commonly be misdiagnosed as disease or bug damage. As temperatures begin to rise, damaged Cedars will begin losing a massive amount of needles. There will be little to no warning as the needles will turn brown and fall almost in the same day. This, understandably, causes great panic in owners. Never fear, there is still hope.
Prevention, Treatment, and Recovery
Preventing winter damage on Cedars can be difficult most years. If the temperatures stay sub-freezing for an extended time, damage is inevitable. However, except for the most extreme cases, a full recovery can be made. Unlike many “needled” evergreens Cedars can regrow needles from damaged branches and twigs. Patience is important in the recovery process, so don’t start pruning just yet. As the temperatures begin to rise you can use your fingernail to scratch a small area of the bark. If there is still life in the branch you will see bright green flesh. If the flesh is brown, the branch has died and you can prune it out. In mid-March feed your tree with Zamzows Thrive. This will give your tree essential nutrients to speed up recovery and rebuild damaged tissue. It will take a few months for new growth to begin. By mid-to-late April you should see signs of new growth. If there are branches or twigs that don’t have any new growth by mid-May you are probably safe to prune it out. You might give it the ole’ scratch test though just to be sure.
Most Cedars can make a full recovery, however, it takes time. Properly feeding and watering over the following season will be crucial to its long-term health. If it is not fed properly, the next winter may be enough to kill it completely.