Oftentimes in the late winter, or even into the spring, conifers begin to turn brown. This browning is a disorder called winter burn. Winter burn results when conifers (especially yews) do not have enough internally stored water for their needs over the winter. As daytime temperatures become warmer in the late winter and early spring, conifer needles begin to naturally lose water (a process called transpiration) as they attempt to grow. During the summer, this lost water would be replaced by water taken up by the plant’s root system. However, in the winter and early spring, soil temperatures are cold enough that the plant’s root system is not functioning efficiently. Thus the amount of water lost by needles is not replenished by the water taken up by the roots. As a consequence, the needles dehydrate and die.
The easiest way to prevent winter burn of conifers is to make sure evergreens are well watered into the fall. Established trees and shrubs need about one inch of water per week. If Mother Nature does not cooperate, then you should apply water at the drip line (i.e., the edge of where the branches extend) of any conifers (or more extensively if possible) using a soaker or drip hose. Conifers can be watered up until the time when the ground freezes or there is a significant snowfall.
With just a little effort in the late fall and winter, you can have a big impact on the health of landscape ornamentals next spring and summer. So get back into the gardening mode, and use the remaining snow-free days of this year to prepare your garden for a beautiful and healthy coming year.
– Brian Hudelson, Director, Plant Disease Diagnostic Clinic, University of Wisconsin – Madison/Extension
Posted by Vicki