March 27, 2001

Discoloration of Evergreens Common This Spring

Reddish-brown, dead foliage in conifer (evergreen) trees is being seen in many home landscapes and shelterbelts this spring. This discoloration is usually the result of injury sustained last fall or during the winter, according to a forestry specialist at North Dakota State University.

"The injury usually occurs several months before the symptoms become evident, and even though proper tree maintenance during the spring and summer may improve new growth, only time will tell how well trees will recover," says Marcus Jackson, forester with the NDSU Extension Service.

Winter discoloration in conifers is often only an aesthetic problem, but it does stress plants and occasionally kills trees, he says.

The injury may result from drying of the foliage or an early fall freeze, Jackson says. Drying occurs when the ground contains inadequate moisture or when the ground is frozen. Trees are unable to take up enough moisture to replace water lost by the foliage. Early fall or late spring freezes can also kill evergreen foliage when it is not sufficiently hardened off.

Discoloration can be greater in trees that were improperly planted, stressed by insects or disease, or improperly fertilized. Some trees may have poor winter hardiness.

Many factors may influence the pattern of injury. Wind can accelerate water loss from needles, so drying is often most evident toward prevailing winds. Damage may be greater near light colored surfaces, such as white siding or white rock mulch. Snow insulates needles, so damage may occur only above the snow line.

Winter drying and early fall freezes kill foliage but cause less damage to buds and branches, Jackson says. Damaged needles often remain green as long as temperatures are cold, then turn brown with warmer late winter or early spring weather. New foliage usually emerges later in spring or early summer. The amount of injury can only be determined after new growth has occurred.

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Source: Marcus Jackson, (701) 231-8478, mjackson@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu