Now that the leaves have changed and begun to fall, many of us have or are starting to put our gardens to bed for winter. While getting the garden ready for winter, spend a little time preparing your trees and shrubs too. Doing a few things this fall can help protect our trees and shrubs from damage this winter.
To help prepare trees and shrubs for the coming winter they should be watered (if we don't get enough rain) so that the soil is moist 8-12 inches deep, until the ground freezes. Watering trees and shrubs before they go dormant will help reduce their stress. This is especially important for evergreens and newly planted trees. Evergreens keep their leaves year round and they are more likely to suffer winter desiccation (also known as winter burn). Desiccation is caused when plants lose moisture faster than they can take it up. This will result in discolored and damaged plant leaves and tip dieback. Having well-watered trees and shrubs and adequate soil moisture can go a long way in preventing winter desiccation. Additionally, roots surrounded by moist soil are less likely to suffer cold injury compared to those in dry soils.
Mulching trees and shrubs is also beneficial when preparing them for winter. Mulch will help retain soil moisture and help prevent rapid fluctuations of soil temperature. Organic-based mulches, such as wood chips, are preferred because in addition to the above benefits they will also slowly break down and add nutrients to the soil. When applying mulch put down a 2 to 4-inch deep layer, ideally out to the drip line of the tree. There should be a 2-inch gap between the tree trunk and the mulch (mulch should look like a donut, not a volcano). Mulch piled up against a tree trunk creates an ideal environment for diseases, insects, and rodents.
Shrubs that are in very exposed sites may benefit from additional protection. These plants can be wrapped loosely in burlap or a windbreak can be constructed. Anti-transpirants are commonly recommended to help prevent desiccation. These products are wax-like materials that are sprayed on to the leaves of plants to help prevent them from drying out. These products don't last very long so they will need to be reapplied several times during the winter (read label directions). While they may help (many studies have shown they are ineffective) in preventing winter desiccation, they aren't a replacement for making sure your plants are well watered and protected if they are in exposed locations.
While people are out cleaning up the garden there is often a temptation to prune trees and shrubs. Pruning in late summer and fall will often encourage plants to produce new growth. This new growth won't have enough time to harden off before winter arrives and will be damaged or killed. The only pruning that should be done on trees and shrubs in the fall is to remove dead or damaged branches. Otherwise wait to do any other pruning, such as removing crossing and rubbing branches, until the trees are fully dormant (late winter is a good time).