Winter Damage on Trees

Winter can be tough on trees, both newly planted and established.  Winter conditions can cause damage in several ways. Conifers and other evergreen plants are particularly prone to damage over the winter.  Often the damage that occurs over winter does not become apparent until the following spring.  Some symptoms you might see are needle browning (sometimes yellowing), cracking or death of the bark, and animal feeding.

Winter Browning of Conifers  |  Sunscald Injury  |  Animal Damage  |  More Information

Winter Browning of Conifers

Dead branch tip on bristlecone pine.
Dead branch tip on bristlecone pine.

Winter browning is often referred to as desiccation injury. On sunny, windy days during the winter when temperatures are above freezing, needles lose (transpire) water. If the soil is frozen, the transpired water cannot be replaced and the tree suffers desiccation stress (needle browning and tissue death). However, water loss alone in midwinter is not the only cause of needle browning. A combination of environmental stresses can cause needle browning on conifers. Winter browning may result from the interaction of extreme low temperatures and frequent fluctuations between freezing and thawing. These conditions are usually found on the south or southwest side of conifers since those areas generally receive most of the sunlight during the winter months. Damage may also appear on the windward side, which may be to the north. Dry conditions during the previous summer months may also be a contributing factor to damage because trees went into winter already stressed.

Make sure all newly planted trees are watered when the orignial rootball or the surrounding soil is dry.  Continue watering from planting until the ground freezes in the fall.  Trees in the landscape for less than five years are also prone to winter browning due to dry soil conditions.  Water during dry periods, especially in fall, for these trees as well. 

White pine sample showing browning of needles from winter drying.
White pine sample showing browning of needles from winter drying.

Avoid pruning browned, burned areas from evergreen trees and shrubs in the early spring since these branches may still have viable buds that will produce new foliage when growth resumes. If the buds did not survive, prune dead branches back to living tissue. Some plants may appear to be fine for a while, and then begin to decline when conditions become stressful in the summer. This may be evidence that there was some root damage.

Proper placement of winter injury sensitive plants, such as yew or arborvitae, can reduce the chance of winter damage. Avoid planting them on the south or southwest side of buildings or in exposed areas. Constructing a physical barrier can also protect the plant from the elements.

Sunscald Injury

Sunscald injury on tree
Sunscald injury causes elongated cracks in the bark, especially on young trees with smooth bark.

Sunscald injury is characterized by an elongated, sunken, dried, or cracked area of dead bark, usually on the southwest side of a tree. The precise cause of sunscald is not well understood.  It is typically attributed to temperature fluctuations.  On cold days, the sun can warm the bark to the point where that area unfreezes. When the sun sets or is shaded by clouds, the active tissue refreezes and dies. Young trees, newly planted trees, and trees with thin bark are most susceptible to sunscald.

Trunks can be wrapped in the fall with tree wrap or plastic tree guards in an attempt to prevent sunscald. Remove the protective covering in the spring.  The most reliable ways to reduce the incidence of sunscald is to leave lower branches on trees for as long as possible, avoid unnecessary wounding of the trunk, and prevent drought stress by properly watering young trees for the first two to five years.

Animal Damage

Besides environmental stresses, mice, rabbits, and deer can cause severe damage to plants in the winter. Animals can girdle trees and shrubs and eat shrubs down to the ground when food supplies are low during a harsh winter. Placing a mesh cylinder made of hardware cloth around the trunk can protect trees. The cylinder should extend 2 - 3 inches below the soil line for mice and 18 - 24 inches above the anticipated snow line for rabbit protection. Be sure the mesh cylinder is in place before the first snowfall and remove the cylinder in spring.  Do not leave the mesh cylinder on all year.  Leaving the metal mesh wrapped around the tree can restrict growth or cause girdling.  Chicken wire around trees will protect them from rabbit damage. Deer can be excluded by fencing, but it must be well constructed and high. Repellants may also be used to give woody material an undesirable taste or smell. Animals may not be deterred by repellents if feeding pressure is high. Supplying animals with supplemental food may be effective in preventing damage to plants. However, be aware that this method may attract more animals to the area.

rabbit damage to tree
Rabbits cause extensive damage to trees when they eat the bark off young trees in the winter.

Do not treat areas on trees damaged by animals with wound dressing or paints.  Provide adequate moisture through the spring and summer and monitor closely as these areas are more likely to see secondary damage from diseases or insects.  If the animal damage was extensive enough, especially if the damage fully circles and girdles the tree, it will likely not survive.

More Information

Last reviewed:
November 2023