At this time of year, when the leaves are changing colors it is important to properly water trees and shrubs to help prevent damage in the winter.
In early fall (mid September) you should stop watering trees.The trees will still be actively growing in September and added moisture will slow the onset of dormancy which is the process that allows trees to prepare for the frigid temperatures in the winter. If trees are not able to go dormant before a heavy frost, tender new growth can be damaged.In the case of fall 2009 here in Calgary, we saw widespread damage due to warm fall temperatures and late and sudden freezing that caused some major die-back in trees and in some cases tree death.
Once the deciduous trees have lost their leaves in late fall (late October), it is time to water again. Deciduous trees will need one final soaking so the root system is moist when it freezes. This ensures the tree is not in need of water going into winter and it will also be available in the spring when the ground begins to thaw.
Evergreens will definitely need to be watered in late fall. These trees and shrubs don’t go into full dormancy. They will constantly be using water anytime the temperature gets near 0′c.
Water deep with the water on low to eliminate run off. Let the water soak into the soil. Ensure the soil is moist when the ground becomes frozen.
Mature trees should be watered at the drip-line while new trees should be watered at the root-ball.
Knowing the right time to water in the fall can save a lot of trouble in the spring and help ensure you are keeping your trees and shrubs as healthy as possible.