As you know, Denver is known for its 300 days of sunshine and surprising weather changes. Winter creates tree care issues for trees but also treatment opportunities for some tree species.
Winter Kill and Sunscald
Over the last two years, Denver experienced sudden drops in temperature in October. Denverites are in short pants during the day, then grabbing heavy coats as the temperature drops into the teens at night. It is not the cold temperature that causes damage to trees. Instead, it’s the rapid drop in the thermometer that is the culprit. On a warm day, the hot Sun causes tree cells beneath the bark to become active. At sundown, the temperature drops, and since the cells did not have the time to return to dormancy, they freeze and die, injuring the tree.
Symptoms of “winter kill” include brown or black discoloration or limpness in branches and leaves. Sunscald is another type of winter kill affecting tree trunks and large branches. Overtime, breaks in the bark occur, exposing the tree to the elements. Ross Tree uses light-colored wraps for winter protection. We wrap the tree in an overlapping fashion from the ground to the first branch. Homeowners, be sure to take off the cover after the last frost in the spring to avoid mold formation.
Fruit Tree Winter Pruning
Winter is an excellent time for pruning because fruit trees are dormant without leaves. It is easy to see the tree branches and decide which tree limbs to remove. A properly pruned tree is less susceptible to mechanical breakage caused by heavy snow. Winter pruning encourages growth because, in the spring, the tree focuses its energy on fewer branches. Trees with an open canopy let in more light and air, which promotes better health and more abundant fruit production.
Winter is also a perfect time to prune apple and pear trees affected with Fire Blight. Since the bacteria are inactive, there is no need to sterilize the pruning tools between cuts. Look for dark blight twigs and cankers. The blight twigs, branches, and cankers are black and easy to spot. The best treatment for a tree infected with Fire Blight is situational, and there are many options. We recommend calling a professional tree service company, like Ross Tree, for the best possible treatment result.
Trees with shallow root systems, such as Birches, various Maples, Lindens, Willows, and Mountain Ash, need winter watering to maintain their health. Also, Spruce, Fir, Boxwoods, and other Evergreens trees and shrubs could benefit from watering. Homeowners with large trees in need of winter watering should consider calling Ross Tree. We have the winter watering equipment necessary to get the correct amount of water to each tree’s root system. Ross Tree suggests the following winter watering guidelines:
- Water only when temperatures are above freezing and the ground is not frozen. Water during the day so the water has time to soak into the ground and reach each tree’s root system.
- Newly planted trees take about a year or more to establish their root systems, so they need supplemental moisture in the winter to avoid root damage.
- Apply 10 gallons of water for each inch in tree diameter.