I have 2 large Yews in my front yard that sustained rust damage over the past...

Asked June 12, 2014, 11:35 AM EDT

I have 2 large Yews in my front yard that sustained rust damage over the past couple winters. There are signs of growth in places, but not everywhere. Should I cut off the rust, trim the bushes back or what would you recommend?

Ramsey County Minnesota yew dieback

1 Response

Thank you for the question. A large proportion of evergreens were harmed by weather last winter. By now, the areas that are going to recover will have bright green growth so prune out the dead branches now. Browning of evergreen foliage during winter occurs for four reasons: (1) Winter sun and wind cause excessive transpiration (foliage water loss) while the roots are in frozen soil and unable to replace lost water. This results in desiccation and browning of the plant tissue. (2) Bright sunny days during the winter also cause warming of the tissue above ambient temperature which in turn initiates cellular activity. Then, when the sun is quickly shaded, foliage temperature drops to injurious levels and the foliage is injured or killed. (3) During bright, cold winter days, chlorophyll in the foliage is destroyed (photo-oxidized) and is not re synthesized when temperatures are below 28° F. This results in a bleaching of the foliage. (4) Cold temperatures early in the fall before plants have hardened off completely or late spring after new growth has occurred can result in injury or death of this non acclimated tissue. To prevent this browning of evergreens, it is important to keep them well watered until the grown freezes in late fall. There are other ways to minimize winter injury. The first is proper placement of evergreens in the landscape. Yew, hemlock, and arborvitae should not be planted on south or southwest sides of buildings or in highly exposed (windy, sunny) places. A second way to reduce damage is to prop pine boughs or Christmas tree greens against or over evergreens to protect them from wind and sun and to catch more snow for natural protection. Winter injury can often be prevented by constructing a barrier of burlap or similar material on the south, southwest, and windward sides of evergreens. If a plant has exhibited injury on all sides, surround it with a barrier, but leave the top open to allow for some air and light penetration. http://www.extension.umn.edu/distribution/horticulture/DG1411.html http://www.extension.umn.edu/yardandgarden/ygbriefs/P466winterinjury.html