Evergreen plants, which retain their leaves (or needles) throughout the seasons, are some of the showstoppers of our landscapes in winter. They provide some much needed color in a world devoid of the green, chlorophyll-laden foliage we have throughout the growing season. Although evergreens do go into dormancy during winter, much like their deciduous cousins, their foliage is still subject extreme exposure over the winter months.
As winter winds constantly strip needles of moisture, soil water is sometimes in short supply to replace what is lost. Some of this limitation is due to the fact that soil water is tied up or frozen within the soil prolife, but it can also result from a general lack of precipitation or dry intervals that occur over winter. If plants cannot replace lost moisture in needles or leaves, then foliage will begin to show signs of desiccation in the form of brown, dead foliage. This type of damage will begin as brown discoloration on needle or leaf tips and may progress as winter continues to include completely brown or dead foliage on entire limbs. It is often confined to the more exposed side of the plant, which is a major clue that winter injury is to blame.
Another cause for winter damage, especially on needle-bearing evergreens, is from road salts. This type of winter injury presents itself very similar to wind exposure, beginning with brown needle tips which may progress to entirely dead branches. It can be the result of salt spray from traffic or the infiltration of salt-laden runoff into the soil profile.
Soil contamination from salt, although rare, is a more extreme condition and may require additional steps to remediate the damage, not only to plants, but to the soil itself. It is generally more uncommon since most roads drain well and it’s not typical for excess water in roadways to heavily inundate landscaped areas.
More commonly, evergreens are damaged from the salt spray generated by traffic near the plants. Similar to wind exposure, this type of damage presents itself on the roadside area of the plant. You can normally identify it from a consistent pattern across many evergreens along the roadway. Most plants will only exhibit dead foliage from a similar height downward. This is because the salt spray can only waft so high as it drifts from the road, resulting in a consistent drift height and equally consistent plant damage.
It is important to realize that plants showing signs of dieback prior to winter are experiencing other environmental stresses or pathogens. Thorough investigation of the cause is needed prior to treatment. Although winter stress may have contributed to the symptoms we are seeing now, it is vital to identify the root of the problem prior to any treatment efforts.
If you have winter-damaged evergreens, the problem can often be easily fixed by pruning out the dead material. However, evergreen plants respond differently to pruning based on the growth habit and needs of individual species. Certain evergreen species, such as pine and spruce, lack interior or secondary buds that will be stimulated to grow after the dead tips are pruned off. In these cases, I recommend waiting another month or so to be sure any dead-looking limbs are truly gone. Although needles may be entirely dead, there may be live buds on the stem that with produce new growth as the growing season progresses.
If you are just dying to know now, there are a few simple tests to identify live twigs versus dead twigs. Since a twig has very thin bark, it is easily scraped away with your finger nail. Scrape away a small section of bark and look for green coloring. Green interior bark indicates the twig is still alive. If you see brown or gray, consider that limb a goner. Similarly, individual buds can be removed and carefully bisected to look for green plant parts. If you can find succulent, green plant parts inside the bud, then there is still hope.
Although minor instances of winter injury can be pruned out, homeowners should still be concerned about the damage and look for ways to mitigate future winter injury. In highly exposed areas I have seen a number of interesting and creative ways to block either wind or salt spray, from makeshift temporary screens to installation of permanent fences. Consider watering plants in winter time to be sure soil moisture is available.
In some years, there is just no avoiding extreme winter conditions, but with some attention during the season and follow-up in spring, your evergreens can flourish for years to come.