Home Grown
Oklahoma winters can be very unpredictable, and a dry winter can leave trees stressed and struggling the following spring. Trees are a long-term investment and valuable part of our landscapes, so preparing them for winter is key.
Tree roots stay active during the colder months and therefore they need moisture to survive. Dry, frozen soil can damage roots, while moist soil holds more heat and offers better protection. And since most tree roots grow within the top twelve inches of soil and extend well beyond the tree’s branches, proper watering is important. The best method is deep watering—slowly soaking the soil to a depth of twelve inches around and just beyond the dripline of the tree. Watering only at the base of the tree or applying water too quickly encourages shallow rooting. And, depending on your landscape, the water might just run off the intended site, which in turn wastes water.
In addition to watering, several other tasks can support tree health going into winter. Applying two to four inches of mulch under the canopy helps conserve moisture and regulates soil temperatures to some degree. Be sure to keep mulch away from direct contact with the trunk and avoid creating a “volcano” of mulch around the tree trunk.
Avoid fertilizing if a tree is under drought stress, and high-nitrogen fertilizers should not be used late in the season. Also, removing dead or weakened branches through proper pruning reduces stress and helps prevent pest and disease problems.
Young, thin-barked trees such as maples, lindens, and fruit trees are especially vulnerable to a type of winter damage called southwest injury. This occurs when the sun warms the bark on mild winter days, followed by a rapid nighttime temperature drop. The repeated cycle of warming and freezing can cause the bark to split, leaving the tree open to pests and disease. I see this issue a lot in landscapes. So, one of the simplest ways to prevent this type of injury is by wrapping the trunk. Tree wraps are usually made of paper or plastic material and applied in late fall after leaves drop. Begin at the base of the trunk and wrap upward, overlapping slightly, until you reach the lowest branches. The wrap should be snug but not tight and removed in early spring once the danger of freezing has passed. Leaving wrap on too long can trap moisture and harbor insects.
With deep watering, mulching, and careful maintenance, your trees will be better prepared to withstand the challenges of winter and remain healthy for years to come.
For more information on this or any other horticultural topic, you can contact Laura Payne, the Horticulture Educator in the Payne County Extension office. Laura can be reached via email at laura.payne@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, at 315 W. 6th in Stillwater.