Desiccation occurs when water leaves the plant faster than it is taken up. Several environmental factors can influence desiccation. Needles and leaves of evergreens transpire some moisture even during the winter months. During severely cold weather, the ground may freeze to a depth beyond the extent of the root system, thereby cutting off the supply of water. If the fall has been particularly dry, there may be insufficient ground moisture to supply the roots with adequate water.
Water loss is greatest during periods of strong winds and during periods of sunny, mild weather.
The heat of the sun can cause stomates on the lower sides of the leaves to open, increasing transpiration. Injury due to desiccation is commonly seen as discolored, burned evergreen needles or leaves. It is worst on the side facing the wind. This can be particularly serious if plants are near a white house where the sun s rays reflect off the side, causing extra damage. Proper watering can is a critical factor in winterizing.