Hello Barbara,

Thank you for contacting the UVM Extension helpline.

Wrapping your arborvitae trees can help with deer damage prevention and from wind and sun damage. Even though your trees are not young, if you still have a presence of deer, they could still damage your mature trees. It takes a bit of work to wrap/protect them and also could take work to help them recover if they get eaten again. Despite being mature, some branches may not recover from being eaten and may need to be removed. One thing to consider is if deer are still an issue in your area and if so weighing the wrapping effort versus mitigation effort if they do get eaten. You may also consider the location and if they get a lot of wind, though it sounds like the deer were your initial reason for wrapping them.

There are several different ways to wrap or protect your trees. You could try a different method this year to see if it helps with the die off. Wisconsin Horticulture discusses ways not to wrap your trees. They say, “DO NOT tightly wrap individual plants with burlap as this can collect ice, trap moisture and make plants more susceptible to infection by disease-causing organisms.” So, if you have been wrapping them tightly, try wrapping them looser this year. They also provide an example of using stakes to create fenced barriers. If the fenced barrier isn’t tall enough it may not protect it from the deer though.

One UNH extension article recommends installing fencing around susceptible plants; however, that may not be practical in this situation. They also suggest trying deer repellants, though note they have mixed degrees of effectiveness. A University of Minnesota Extension article discusses additional ways to protect plants from deer as well as protecting plants and shrubs in the winter. Another page from University of Minnesota provides information on different ways to protect trees and shrubs in the winter and may give you some additional ideas.

You mentioned using plastic and will just want to avoid using black plastic as it causes extreme temperature fluctuations. In general you want to avoid wrapping a tree with plastic as it also may not allow as much breathability.

I’ve included a couple of additional Extension resources below:

Do My Evergreen Shrubs Need Winter Protection?

Build a Better Windscreen for Evergreens this Winter

Good luck with whatever you decide to do!