All trees and shrubs are susceptible to winter desiccation, but evergreens often suffer more than other plants. This is a common injury that occurs when the amount of water lost by the foliage exceeds the amount of water picked up by the roots. Even though plants go dormant in the winter they still need water. And because evergreens hold onto their needles they need more water than deciduous trees. Radiant heat, warm sunny days, or windy conditions increase the amount of water lost from the needles. If the soil is dry or frozen plants cannot pick up enough water to meet their needs and the needles dry out and die. The extent of the damage can vary from needle tips, to branches to the whole plant dying. The injury is more noticeable come spring.
Another factor that contributes to plant injury is reflective heat from hard surfaces like retaining walls, brick siding, or rock. Plants planted facing prevailing winds and sunlight, can also suffer from exposure.
To help your trees and plants through the winter months give them a thorough soaking in late fall, and periodically during the winter, when possible. A slow, deep watering with a hose trickling for an hour or so will help moisture be available to them. Other factors also influence plant health. Drought stress, girdling roots, poor planting or planting in the wrong place are all contributing factors. Mulch around the base of trees will also help conserve soil moisture and help prevent deep freezing.