Winter injury on spruce trees is very common across Wyoming. The typical symptom of winter injury on spruce is purple, tan, or brown discoloration of the needles appearing in spring. Often times existing needles show symptoms, but buds survive. Those buds can give rise to new growth and improve the plant’s appearance during the next growing season. In severe cases, trees may not recover. Winter injury can be the result of extreme cold temperatures, drought stress, winter desiccation (cold dry winds draw moisture out of the needles when the ground is frozen and roots are unable to replace moisture to the needles), or a combination of these problems. Symptoms generally appear in winter and spring. Spruce trees infested with aphids or pine needle scale can increase spruce tree susceptibility to winter injury. Monitor for these and other pests and treat as needed.

Irrigating adequately is the best recommendation to prevent winter injury and to help trees recover following winter injury, although severely affected trees may not recover or improve in appearance even with supplemental water. Spruce trees should receive irrigation year-round. Water trees regularly throughout the growing season until the ground freezes in fall and water occasionally in winter during a thaw. While watering with a drip line can be sufficient for a newly planted tree with a very small rootball, drip irrigation is often inadequate for larger trees. Hand watering with a hose or overhead sprinklers will do a better job of irrigating large areas.

In addition to irrigation, proper planting, spacing, and maintenance practices can help keep trees healthy and less susceptible to winter injury and other stress. Trees should be planted at the proper depth. Trees planted too deep will suffer from lack of oxygen and trees planted to high will suffer from dehydration. Trees planted too close together will crowd each other and compete for water, nutrients, and light. Lower branches on spruce trees help shade and cool the tree’s relatively shallow root system. Limbing-up spruce trees is not recommended because removing lower branches exposes the roots to higher temperatures and causes the soil to dry out quicker. Mulch rings around the trees will help soils retain moisture. Also, avoid growing turfgrass around the base of spruce trees. Grass will compete with the tree for water and nutrients which can be extremely problematic for young trees.