No doubt many of you reading this recall the extraordinarily high incidence of winter injury on confers revealed last spring with lots and lots of brown pines and spruces.
Winter injury can happen on any tree species and include things like tip die back, frost cracking of the trunks and browning needles on conifers.
Brown conifer needles typically receive the most attention as is understandable with the unsightly brown contrasting the healthy green. Unfortunately by the time the needles turn brown and alert attention, the damage has been done.
Conifer needles, even in the dead of winter use water. When the stored water in the twigs and needles is depleted, the needles get dehydrated and eventually die. Certain factors exacerbate this process, drying winds, warming day time sun, de-icing salt as well as drought conditions during the previous summer and fall. Aspect is another factor in the severity equation. Winter burn usually occurs on the south and west facing sides of the trees.
The warm sun exposure during the day can break dormancy and cause the needles to thaw. When the sun sets in the evening, the rapid freeze can cause tissue death.
There are a few things you can do now to reduce your risk for winter burn.
• Avoid using de-icing salts near conifers, if you do use them for safety reasons rinse them off of the evergreens after spring thaw.
• Erect protective barriers to block wind and insulate needles from thawing on warm sunny day. You can wrap burlap, or use plywood to serve as a barrier.
• In the future avoid planting arborvitae or yew species on south west sides of buildings or in open areas with full sun and strong winds.
• To the best of your ability provide supplemental water to vulnerable conifers next fall to maximize the amount of water stored in their twigs and needles.
Sources: University of Minnesota Extension Service & Minnesota Dept. of Natural Resources
If you have tree health related questions you may contact Gina Hugo with the Sherburne Soil & Water Conservation District at firstname.lastname@example.org or by calling 763-241-1170 ext. 4.