Winter burn is discoloration resulting from plants not able to take up moisture from the ground because the ground is frozen through the winter months. This causes the leaves or needles of evergreens to dry out.
During the cold months, evergreens continue to lose moisture through their leaves (or needles). The leaves must replace the water by pulling it up from the roots. But when the ground is frozen, the plants' roots cannot absorb water to supply it to the leaves. If the weather turns warm and sunny while the ground still is frozen, evaporation from the leaves increases and the water cannot be replaced. Discolored or "burned" foliage may start to appear.
Anything that dries out evergreen leaves can cause winter burn. Since salt draws water from plant tissue, salt spray from traffic can cause winter burn in evergreens near driveways or streets. Hot air from dryer vents or furnace vents also can dry out nearby plants. Winter burn symptoms typically develop during warm weather in late winter and early spring.
The brown or yellowed foliage generally is on the side of the plant facing the sun and/or the side exposed to the wind, where the rate of evaporation from the needles or leaves is greatest.
Winter burn can be more prevalent in years in which the ground freezes early before plants are acclimated to cold weather or when there is little snow. Without snow cover or mulch to insulate the soil, the ground can freeze more deeply.
If you see winter-burned foliage in spring, it is best to be patient and wait for new growth. Once the new growth comes in, you can trim out the dead plant material. Make sure plant is well water and mulched.