Winterizing Evergreens

Winter can wreak havoc on evergreen landscape plants, but some simple steps taken in the fall can help protect them. Evergreens tend to be relatively expensive investments compared to other plants, so helping them avoid winter damage is important.

Arborvitaes are vulnerable to splitting from heavy snow and ice loads, especially individual plants which have multiple leaders. Once the branches splay apart or bend down for long periods under a heavy weight, it's unlikely that they'll regain their attractive, compactly upright shape. This can ruin the appearance of the evergreen, and if it happens to even one out of a hedge, finding a replacement of the same size can be costly or impossible. When the brown interior foliage is exposed, the plant is especially unsightly.

To avoid splitting damage, tie the branches together in late fall, before snow arrives. Using strong twine or plastic coated wire, tie multiple leaders together, but don't squish them tightly; allow them to remain a few inches apart. Do this work from the inside of the plant, so that the twine remains invisible, do not wrap it around the outside. While this prevents splitting, unfortunately, a very heavy snow can still bend the entire plant over.

Winter burn is the other common killer of evergreens and it ruins both needled and broadleaf evergreens like rhododendrons. Most gardeners don't think about it, but sunny winter days are as dangerous to evergreens as the cold, windy ones. Moisture loss is the cause of winter burn. When the ground freezes, the plant roots aren't able to pull water up into the leaves. When either sun or wind causes transpiration, moisture is drawn out and can't be replaced. Salt spray is also a huge threat.

Several brands of anti-desiccant sprays, such as Wilt-Pruf, Vapor Guard and Transfilm are available at garden centers, and some landscape maintenance companies offer application service. These products are waxy coatings which remain on the plant for weeks, and they stop excessive moisture loss. Proper application isn't difficult, and the products aren't toxic, but directions must be followed carefully. The sprays have to be applied when it's above 40 degrees and should be done early on a sunny day to give the spray time to dry. Late November is a good time, if weather conditions allow. After several weeks the coating will wash off and reapplication is necessary. Remember that very late winter is the most problematic time because warmer, windy days come along to dry out the leaves, but the ground may still be frozen.

Homeowners commonly resort to erecting burlap or landscape fabric shields or various types of teepees over choice evergreens to keep salt, snow and ice from causing damage. This works, but then the winter beauty of the plant is hidden, and winter interest is one of the main features of evergreens. If evergreens are close to a heavily salted road, this might be the only solution.

As for some things not to do: Never wrap plants in plastic. This is a killer. Don't prune in late summer or fall because pruning forces new growth which won't have time to harden off before your evergreens face winter.