Boxwood winter burn usually occurs when there are warmer than normal winter day time temperatures. The warm day time temperatures allow the plant to partially come out of dormancy. When the plant comes out of dormancy, the plant tissue begins to fill with water again. When temperatures during the night-time drop below freezing, the thawing process stops and the water in the plant tissue freezes. When the water turns to ice, it expands and ruptures the plant tissue. This split causes boxwood winter burn by killing the tissue of the plant. On the other extreme, cold dry winds can pull moisture from the plant causing branches to die out. There is a wide variety of damage that can occur in boxwood winter burn. Tip damage to the plant is most common. You will usually see yellowing or whitening of the boxwood leaves. In some instances you may encounter entire branches or sections of the plant dying out. Most extreme conditions are caused by a huge fluctuation in temperatures from day time to night time.
How to remove boxwood winter burn.
If you have newly an installed boxwood plant that suffer from extreme winter burn, it is probably best to replace the plant. If have a mature plant with extreme winter burn, pruning may help your plant recover. In some instances the dye-back is too severe to be pruned. You will have to determine if the plant is worth you time and effort to save it. Boxwood winter burn can also be minor. Minor winter burn is usually yellowing of the tip of the plant. If the tips or full branches of the plant turn white, then they are too far gone to save. Some of the yellowing will recover when temperatures warm up and stabilize. If there is extensive yellowing, it may be necessary to prune out the dead or damaged part of the plant. Most boxwood winter burn will go away in the spring with some minor pruning.