Winter Prep for Trees (09/23/21)
This past year has been extremely tough on trees, especially in central North Dakota where the drought has been exceptionally bad. Some trees are doing okay, others are struggling, and some have already succumbed to a combination of drought, insects and/or disease. For the trees that are surviving, the dormant season will come with its own challenges. However, there are some management actions that we can take now to help trees survive the winter and even thrive next summer.
All trees could use some water, but it’s even more critical for conifers that they go into winter fully hydrated. Conifers that are drought-stressed are more prone to the type of damage that is generically called ‘winter injury’. Winter injury takes many forms and has several potential causes; nevertheless, studies have shown that trees that are well-hydrated going into winter are less likely to suffer damage over the cold season. Watering should get the soil moist, but not saturated, to as deep as you can get it. Remember also that tree roots extend far beyond the edge of the tree crown. The larger the area that can be watered, the better.
Foliar diseases haven’t been as prominent this year because of the drought. However, if your trees had foliar fungal problems such as frogeye leaf spot, apple scab, oak leaf blister, or one of the anthracnose diseases, then be sure to rake up and remove or destroy all the fallen leaves this autumn. The fungal spores over-winter in the fallen leaves so getting rid of this source of inoculum will go a long way towards preventing foliar diseases next year.
Finally, make sure to protect the stems of young/small trees from the various ravages of winter. Often, this means putting some type of white wrap or corrugated white pipe on the stem to help prevent sunscald (another form of winter injury). Perhaps more importantly, these products can help prevent damage from deer, rabbits or voles. Make sure that the wrap goes high enough that it will reach well beyond the expected snowpack, as rabbits can climb the drifts and girdle stems or even branches of deciduous trees. Sometimes, it may even be better to place a fence further out from the stem, to keep the deer away from the branches.
NDSU Extension Forestry Specialist