We have eight large thuja evergreens behind the house, each about 7′ tall and each 5 years old. This spring, all their edges have turned brown, the new top spikes are brown, and the trunks appear mottled. Are they dying from the unusual winter (freeze/warmth/etc.), and can they be saved? Please help; they are our privacy border.
The Gardener’s Answer
Hi, Mary in Kentucky: There are a few different possibilities when it comes to the tips of evergreens defoliating. The most common would be due to winter burn; this occurs when the new growth is not hardened off in the fall before the winter arrives and this tender growth is essentially burned by the winter temperatures and wind. It also happens if the evergreens go into the winter months without sufficient moisture. If you had a dry fall and the ground froze, the plants would not be able to uptake any water and as a result the tips would burn. Arborvitae are susceptible to a few different fungal problems, including twig blight. Did you notice any fungal spores on the branches or the foliage? If so, you should take a sample to your county Cooperative Extension Service for the horticulture agent to get a positive diagnosis. All plants, including arborvitae, are more prone to insect and disease problems when they are stressed. If they are not giving optimal growing conditions this can result in stress and lead to health problems. Arborvitae prefer to grow in full sun to part shade with nutrient rich soil. Thuja occidentalis (Eastern arborvitae) are more tolerant of poorly drained soil but most prefer soil that is well-drained. The best thing to do now is to have a horticulturist take a look at a sample of your evergreens to determine what is going on and from there they will be able to give you the best treatment options. The Grayson County Web site is http://ces.ca.uky.edu/grayson
or you can reach them at (270) 259-3492.