Evergreen trees are a great feature for any landscape, adding reliable, year-round interest. They're tough trees, with their leaves and needles clinging on even through our frigid North Dakota winters. But even evergreens are susceptible to winter burn, which turns their lovely green needles into dull, rusted tips. Luckily, winter burn on evergreens is easy to treat and even easier to prevent. Add a few simple tasks to your autumn chores list to keep your trees bright and bushy all year long.
What Causes Winter Burn on Trees?
The idea of burn from the cold might seem contradictory, but similar to freezer burn on leftovers that were in the freezer too long, freezing temperatures do have a cold burn effect. In addition to the cold air, harsh winds and low soil moisture all work together to cause winter burn on trees.
Since they hold onto their leaves and needles, evergreens are always losing moisture, even during dormancy. But with dry air, frozen ground, and harsh winds, there's very little moisture available to evergreens at this time. These harsh weather conditions also increase the rate of transpiration, which leads to your evergreens losing moisture faster than their roots can replace it from the frozen ground.
How to Spot Winter Burn
Although the presentation differs based on the plant, winter burn isn't difficult to identify. The most obvious sign of winter burn is the discoloration of the foliage, which starts on the outer branches and works its way in towards the stem or trunk as the problem worsens. For needle evergreens, the discoloration will start at the tip of the needle and move towards the base. For broadleaf evergreens, it will begin at the outer margins of the leaf before spreading inward.
Most often, winter burn turns the gorgeous green foliage we love into an unpleasant, rusty color. Some evergreen trees might also display shades of yellow, red, or brown. You'll notice that damage is more severe on the side of the tree that receives sun and harsh winds.
The good news is that winter burn on evergreens can usually be repaired and, most importantly, prevented. But in a severe case of winter burn, the damage might be irreversible. When this happens, make sure you remove and dispose of the tree so it doesn't become an invitation for unwanted pests.
How to Protect Evergreens from Winter Burn
The easiest way to control winter burn is to prevent it from happening in the first place. Prepare your trees for the harsh winter weather ahead by taking simple protective measures before the season arrives. Your trees will thank you for the added protection and reward you with a beaming winter landscape right up until spring.
In the fall, mulch the base of the tree. We use mulch to cover roots and retain moisture during the dry heat of summer, but winter is no different. Just because it's cold, doesn't mean the dry air doesn't suck the water right up from your plants' roots. In the fall, apply a generous layer of moisture around the base of your evergreen trees, leaving some space around the trunk so it can breathe.
Hydrate your evergreens as much as you can before winter arrives. Since the main cause of winter burn is inadequate moisture, we want to get as much water locked into the ground before it freezes. While some people start to slack on watering once the cool autumn air hits, we encourage watering deeply every week through the fall, right up until the ground freezes. To ensure a continuous supply of moisture, consider installing a drip irrigation system. You can even make one on your own - drill some small holes through the bottom of a large barrel and fill it with water, refilling as it gets low.
Apply fertilizers and anti-desiccant spray in late autumn, before the ground freezes. Fertilizers provide your plants with extra energy and nutrients, which helps to keep them strong in stressful conditions. An anti-desiccant spray is applied directly to the needles once in late fall and again during early winter. It helps to keep moisture in the needles, lessening the transpiration that leads to winter burn.
What to Do for Winter Burn
Judging from the harsh winter we've just experienced, winter burn on evergreens might be impossible to avoid. If you did take protective measures, take comfort in knowing that they at least softened the blow for your trees! Luckily, a little bit of winter burn is nothing to worry about, and there ways to repair any damaged branches.
First, check branches that are affected by winter burn to make sure they're still alive. Now that we're well into spring, they should be budding and growing. If there are any tiny buds present, that's a sure sign that the branch is still alive. If you don't see any, scrape away a small bit of bark - if you see green, you're in the clear!
Unfortunately, if there's no sign of new growth and the branch is totally dry, then it will have to be removed with pruning shears. Make sure you're familiar with your specific plants' growth patterns. Evergreens don't all grow back branches the way that deciduous trees do. Cutting branches right down to the base or trunk might leave gaping holes in your tree, which will end up being less attractive than what you started with. A good example is pine trees, which only produce new growth at branch tips. If the branch isn't completely dead, simply brush off some of the discolored needles and leave the rest alone.
Those of us with evergreens standing strong in our gardens adore their tough nature and consistent beauty. But even these durable trees can be damaged by the intense winter weather, and who can blame them? Take good care of your evergreens by taking steps to prevent winter damage and treating them appropriately when it does occur.