Damage from cold temperatures beginning to show up
As the weather warms, some conifers have begun to turn brown due to winter injury.
This winter has certainly been one for the record books. Not only was it cold, but it seemed exceptionally windy. So it isn’t surprising to see conifers beginning to show the classic symptoms of winter injury. Winter injury can affect most Christmas tree species and other conifers. Growers are reporting that they are seeing damage on many species including Austrian, Scotch, and white pine; Colorado blue and Serbian spruce; Douglas-fir, Fraser and Concolor fir.
The most obvious symptom of winter injury is browning needles, especially on the south side of the tree or above the snow line. In addition, buds may be damaged.
The first type of damage we find is often called winter drying. Drying occurs when the soil is frozen and the roots cannot easily replace water therefore, the trees lose moisture in the winter due to windy or sunny conditions.
The second type is referred to as winter burn. This happens when needles or buds are damaged after rapid temperature changes. This most often occurs on the south side of the tree where the sun reflects on the snow and warms the tree during the day and then at night the temperatures drop. In a year like this, growers may be experiencing both winter drying and burn.
To complicate matters, we also see browning on Austrian pine due to Dothistroma needlecast or Swiss needlecast on Douglas-fir. In addition, some trees may have died over the winter from compromised root systems caused by Phytophthora root rot in Fraser fir or pine root collar weevil on several pine species. Once you can get into the field it’s a good idea to look closely at the trees to determine what the true cause is of the symptoms you are observing.
Damage can vary from year to year and site to site. The long-term impact depends on whether or not buds are killed. We can often see needle browning without bud-kill. If buds are injured, it will take longer for trees to recover and will require adjustments in how we shear the trees. To help trees recover, try to minimize any additional stresses this growing season through proper nutrient management, weed control and irrigation.