Cold dry weather can dehydrate the foliage of arborvitae. The dehydration kills the foliage, which turns a light to medium brown color. Plants going into the winter short of moisture are much more susceptible to winter dehydration (burning/scorch/desiccation). In addition, plants being grown in extremely windy locations are also more prone to winter dehydration. If the dehydration is severe, not only will the foliage die but some of the smaller twigs too. As the dehydration worsens, more and more of the plant is killed till the entire plant dies. If only the winter foliage is killed, the plant should leaf out again in the spring. If the woody tissue is dehydrated to the point of death, then the plant needs to be replaced.
Control is to make sure the soil around these plants is properly watered just before the ground begins to freeze. In windy locations, a physical barrier made of burlap, weed barrier fabric, plastic, snow fencing and so forth can be used to break the force of the wind thus reducing the risk of dehydration. In addition, a spray-on anti-transpirant can also be used to reduce moisture loss. In prolong winters; a second application may be necessary. Be sure to read the label before purchasing the product to make you can apply it correctly. Then follow ALL label directions and precautions for the best results and a safe environment.
Written by James Schuster, Extension Educator, Horticulture, and reviewed by Bruce Paulsrud, Extension Specialist, Pesticide Applicator Training and Plant Pathology, University of Illinois at Urbana-Champaign.