By: Ron Honig, Crop Production and Horticulture Extension Agent
As temperatures have cooled, water demand in our lawns and acreages has dropped off significantly. Warm season grasses have gone dormant and our cool-season grasses have slowed their growth to the point of needing only one last mowing.
For our trees and shrubs, however, watering now is important if soils are dry to help alleviate moisture stress. Making sure trees go into the winter with adequate moisture to draw on is important for maintaining tree health. Many of the tree problems I observed in the last few years can be traced back to environmental stress and much of that stress is related to winter neglect or drought conditions.
A good, deep watering with moisture reaching at least a foot down into the soil is much better than several light sprinklings that just wet the top portions of the soil. A deep watering, which may require approximately two inches of water, will help ensure that the majority of tree and shrub roots have access to water. Regardless of the watering method used, soil should be wet at least 12 inches deep. Use a metal rod, wooden dowel, electric fence post or something similar to check moisture depth. Dry soil is much harder to push through than wet thus heavy resistance in the soil is usually an indication you have reached dry soil.
Although all perennial plants benefit from moist soils before winter, it is especially important for newly planted trees and shrubs due to limited root systems. Even trees planted within the last 2 to 3 years are more sensitive to drought than a well-established plant. Evergreens are also more at risk because moisture is lost from the foliage.
Another potential problem to be concerned about during the winter months is sunscald or freeze injury on young or thin backed trees. Trees most often affected by sunscald are young honey locusts, fruit trees, ashes, oaks, maples, lindens and willows.
Trees that have branches growing lower on the trunk are not as susceptible as the foliage and branches provide a natural sun barrier. Sunscald normally develops on the south or southwest side of the tree.
There are two types of sunscald; summer sunscald and winter sunscald. Summer sunscald is caused by the bark reaching temperatures during the heat of summer that kills underlying tissues. This is more of a problem in states that are more southern but includes Kansas.
Winter sunscald occurs during late winter. Sunny, warm winter days may heat the bark to relatively high temperatures. Research done in Georgia has shown that the southwest side of the trunk of a peach tree can be 40 degrees warmer than shaded bark. This warming action can cause a loss of dormancy and cold hardiness of the bark tissue resulting in cells becoming active. These active cells then become susceptible to lethal freezing when the temperature drops at night. The damaged bark tissue becomes sunken and discolored in late spring. Damaged bark will eventually crack and slough off.
Prevention is the best way to deal with sunscald. Applying light-colored plastic or paper tree wrap from the ground to the start of the first branches is recommended to protect recently planted, thin-barked trees. The light-colored material reflects sunlight and the wrap maintains a more even temperature at the bark surface. Usually protecting the tree the first year of planting is sufficient but some trees may need to be wrapped a second year.
The heavier plastic wrapping has a secondary use in that it deters rabbit damage to the bark. Rabbit feeding is common in some areas during the winter months as normal food sources become hard to find, especially during periods of significant snow coverage.
If rabbits are a serious problem in your area, other deterrents might include using at least a 2-foot-tall cylinder of 1-inch-mesh, chicken wire, or similar commercial barrier around the base of the tree. Remove the barrier in the spring or it can be left in place for a time. Just remember to remove it before it starts to constrict the outward growth of the trunk. Other control methods include liquid rabbit repellents sprayed on the plants. Repellents however, will need to be reapplied each time it rains.
