Preventing Winter Burn

Questions arise all times of year concerning brown patches appearing on evergreen trees and shrubs, commonly referred to as “winter burn.”  While most noticed during the spring and summer months, year-round care (including well into the fall) is important to minimize future occurrence.

Winter burn is common in our area and last winter was particularly hard hit, because of the lengthy extreme cold periods along with some midwinter thawing.  While the standard response from landscapers and tree companies is that “it is just winter burn — don’t worry”, that  doesn’t mean that it is not important and that you should ignore it.  If you do nothing for burned junipers, yews, boxwoods and arborvitae the effect can be cumulative, which means the plants may decline year after year until they can’t recover.  The cumulative effects are a bit less severe on pines, spruces and hemlocks, because new growth is produced from the branch tips.

Winter burn is caused by excess moisture loss from the winter sun and wind, so the ‘burned’ needles and branches are essentially desiccated by the elements.  Plant characteristics, exposure conditions, and care all contribute to the effects of winter burn; the problems can be exacerbated by exposure to road salt.

If your evergreens have been burned for several years without extra care, it is possible they won’t recover.  However, here are some things to do to restore their health and minimize future burn:

• Cut out any dead, damaged or brown needles and branches – cut back to a live branch or lateral bud. This should also trigger replacement growth and plant vigor. The best time to cut out damaged branches is mid-spring when the evergreens have just started their own new growth.
• Keep the evergreens well watered – approximately 1 inch of water per week throughout the growing season.
• Continue watering well into the fall until the ground freezes (or the ground is snow covered). If there is a lengthy winter thaw, supplemental watering can help counteract renewed transpiration and photosynthesis.
• Mulch the evergreens to reduce moisture loss and insulate roots
• Do not prune or fertilize in late summer or fall .  This would trigger late growth that is unhardened off before freezing, and those tender growths would be particularly susceptible to winter burn
• Protect exposed plants (especially on south and west sides).  A burlap barrier 5 ft tall just outside the drip line can help (don’t tightly wrap the evergreen)