Preventing Winter Burn on Evergreens: Why Yews and Arborvitae Turn Brown

Winter burn happens when sun and wind pull water out of evergreen foliage while the roots sit in frozen soil. Water well until freeze up, mulch, put up bu...

Published by ThriveThyme

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The Short Answer

Winter burn is drying, not cold alone. On sunny or windy winter days, evergreen foliage keeps losing water, but the roots are in frozen soil and cannot replace it. The tissue dries out and turns brown (UMN Extension, Wisconsin Horticulture).

To prevent it:

  1. Water well in fall. Water thoroughly in October until the ground freezes (UMN).
  2. Mulch. Two to four inches of loose mulch out to the drip line, kept away from the trunk (Wisconsin).
  3. Screen, do not wrap. Put burlap or similar barriers on the south, southwest, and windward sides, and leave the top open (UMN, Wisconsin).
  4. Plant in the right spot. Sensitive evergreens do better on the north or northeast side of a building or out of the wind (UMN, Wisconsin).

If burn shows up in spring, wait until mid spring to prune. Brown foliage will not green up, but buds often push new growth (UMN).

Which Plants Get It

UMN Extension names yew, arborvitae, and hemlock as the most susceptible, though any evergreen can brown. Wisconsin Horticulture adds broadleaf evergreens such as boxwood, holly, and rhododendron, needled evergreens such as fir, pine, and spruce, and scale leaved plants such as juniper and false cypress. New transplants, plants with soft late season growth, and plants that are only marginally hardy where they grow are at higher risk (UMN, Wisconsin).

Why It Happens

UMN and Wisconsin describe a few causes that often stack up:

That is why damage usually shows on the south, southwest, west, and windward sides, while foliage under snow or facing away from sun and wind stays green (UMN, Wisconsin).

Prevention, Step by Step

Water before the freeze

Plants that go into winter well watered burn less. UMN suggests cutting back slightly in September so plants harden off, then watering thoroughly in October until freeze up. It also notes that watering only in late fall does not help much on its own, so steady watering through the growing season matters too. Wisconsin suggests about 1 inch of water a week for established evergreens and up to 2 inches for new transplants, until the soil freezes, using a soaker or drip hose near the drip line.

Our fall and winter watering calculator can help you plan the gallons.

Mulch the root zone

Wisconsin recommends 2 inches of loose mulch on clay soil and up to 4 inches on sandy soil, out to at least the drip line. Keep it at least 4 inches from trunks and stems, since mulch piled against the plant can shelter voles and favor disease. Mulch evens out soil temperature, holds moisture, and helps stop frost heaving. See the Winter Mulch desk for amounts.

Put up a screen

Wisconsin suggests driving 4 to 5 foot stakes about 2 feet out from the drip line on the south and west sides, or any side exposed to wind, and stretching burlap, canvas, or snow fence between them. UMN says the same for the south, southwest, and windward sides. If a plant has been injured on all sides, surround it, but leave the top open for air and light (UMN).

Do not wrap individual plants tightly in burlap. Wisconsin warns that tight wraps can collect ice, trap moisture, and make plants more prone to disease. Take screens down promptly in spring.

UMN also suggests propping pine boughs or old Christmas tree greens over low evergreens to block sun and wind and catch snow.

Skip late pruning and fertilizer

Do not prune evergreens after August, because pruning can push new growth that will not harden off before winter (UMN). Wisconsin adds to avoid quick release, high nitrogen fertilizer in late summer and fall for the same reason.

Plant in the right place

Put yew, hemlock, arborvitae, and other sensitive evergreens on the north or northeast side of buildings, or anywhere sheltered from wind and winter sun (UMN). Wisconsin suggests partial shade for boxwood, hemlock, rhododendron, and yew, and planting evergreens in early spring or late summer so roots can grow before the ground freezes.

What About Anti-Desiccant Sprays?

The two extension sources do not agree on the details, but neither recommends counting on them. UMN Extension says anti-desiccant and anti-transpirant sprays are not effective for protecting evergreen foliage. Wisconsin Horticulture says they have been shown to have limited benefit, break down quickly, need reapplying after each significant rain or snow, and may not prevent the water loss that causes burn. Water, mulch, and screens are the better bet.

If Your Evergreen Already Burned

Do not prune in March. UMN says brown foliage is most likely dead and will not green up, but buds are hardier than leaves and will often grow and fill in. Wait until mid spring, after new growth starts, then prune out what is still dead (UMN, Wisconsin).

To check a branch, Wisconsin suggests scratching the bark and gently peeling back a bud scale. Green tissue means the buds may still break. Brown tissue means that part is dead, so cut back to a live bud or branch. Pines, spruces, and firs usually push new growth at branch tips that replaces burned needles, so they may not need pruning at all.

After a burn, UMN suggests fertilizing in early spring, watering well through the season, and protecting the plant the next winter. If an entire evergreen is brown, Wisconsin says recovery is unlikely and it is time to replace it with something better suited to the site.

Next Steps

Sources