Sunday, January 25, 2015

Brown Needles on Pines May be Due to November's Cold Snap by Mary Small

Photo by CJ Clawson
We are starting to see the first damage to plants caused by the unseasonably cold weather in November. Many evergreens, particularly pine, are now showing injury from the rapid and sustained drop in temperature. Needles are turning a straw to red brown color, depending on the species and location.  Warmer, southern sides of trees are especially hard hit, since those areas had not yet developed complete winter hardiness. 

Photo by  CJ Clawson
Plants develop the ability to withstand cold winter temperatures in response to decreasing daylight and other signals. One of the signals includes exposure to gradually decreasing temperatures. And November’s cold spell was anything but gradual. We descended from early fall temperatures into mid January ones! The temperature dropped 50 degrees in a few hours.

 What can be done now? Water all evergreen root systems monthly in the absence of rainfall or snowmelt.  It won’t reverse the process – the brown needles won’t turn green again- but it will keep healthier portions of the plant hydrated. 

It will likely be mid-spring 2015 before we can begin to assess the true damage from the cold. And like a similar Halloween freeze of 1991, injury may continue to appear for a couple of years.