YES! Evergreen plants are active all year and deciduous ones even without leaves will have their roots growing during fall and winter until soil freezes. So, both plants will need water to perform their activities. Root growth is very very very active in the fall and in early winter, so deep watering is a most!
“Water in the soil, acts as a heat sink that regulates the soil temperature. It keeps the soil from overheating in summer and from getting too cold in winter. It softens and lubricates the soil in fall and spring when roots are putting on the most growth. When it is cold enough, the water in the upper soil layer freezes; this insolates the lower layers of soil from any extreme air temperature fluctuations we might get. Also, when the soil freezes the water expands moving and loosening the soil so when it melts the soil is less compacted. There are many reasons the soil needs to remain moist through the winter”. 1
How to check if your landscape has enough moisture?
Most of the fine feeder roots that are responsible for the uptake of water are located in the top 12 to 18 inches of soil for trees and 4 to 6 inches of soil for shrubs. It’s that area that should be kept evenly moist, letting only the top 2 to tree inches dry out before re-watering. For trees, if the soil in that top 12 to 18 inches becomes too dry, the small feeder roots will die, impairing the tree’s ability to absorb water when it becomes available again, same for the 4 to 6 inches apply on shrubs. Be sure to check the soil moisture to determine when water is needed. You do this with a trowel, shovel, or soil-sampling tool. Don’t rely on the appearance of the soil surface, dig down and feel the soil several inches below the surface.
If your trees are growing in a lawn area, keep in mind that the grass may be using a large portion of water that’s being applied through a sprinkler system. Even if you think you’re applying enough water, check the soil moisture in the tree root zone. Make sure adequate moisture is reaching the soil and tree roots. Consider supplemental watering if your trees need more water. Water your trees before the soil becomes completely dry, but when you water it is best to water thoroughly and then don’t water again until the soil needs it. In the winter the soil should receive a good soaking about every 20 to 30 days. During the summer you may need to water every 5 to 10 days to prevent the soil from becoming too dry. As you get in the habit of checking the moisture level in the soil you will become more aware of the moisture needs and more easily time the watering for the time of year.