This past year has been one of the driest on record. The effect of the drought on crops and livestock is extensive and has been well-publicized, but drought conditions also impact trees.

What can you do now to help assure their survival now and through the coming winter?

“The simplest answer, of course, is to water trees now and keep them well-hydrated right until the soil freezes,” says Joe Zeleznik, North Dakota State University Extension Service forestry specialist. “Tree roots continue growing as long as the soil temperature is above 40 degrees. Therefore, getting water to the trees now is critical for helping them cope with the bitter cold winter temperatures to come. Focus on those trees that are most susceptible to winter injury, which are conifers and newly transplanted trees.”

Tree roots are deeper than those of lawns and are more widespread than many homeowners realize. The watering should be slow, deep and extensive (edge of the drip lines of the trees and beyond). Check to be sure the water has penetrated to a depth of at least 6 to 9 inches.

One rule of thumb is to use 10 gallons of water for each inch of tree diameter (caliper), according to NDSU Extension Service horticulturists Ron Smith and Tom Kalb. They advise watering once per week using nonsaline water and continue watering as long as dry weather persists. Using water with a high salt content can stress the trees even further and cause more harm than good.

Adding mulch around trees also can help keep moisture in the soil and protect the trees from the drastic temperature swings that especially come in February and March.

Place snow fences or other structures in locations that will help capture and deposit snow around the trees. For prize specimens, make sure they’re also fenced in and protected from rabbits and other animals that might climb on top of the snowbanks to eat the tender shoots.

“The drought has been tough on our trees,” Zeleznik says. “Nevertheless, there is still something we can do about it now. Water your trees thoroughly now and through the fall until freeze-up. Doing so will help minimize the stress and damage that winter can cause.”

NDSU Agriculture Communication – Sept. 20, 2012