Notes on Winter Tree Care
Watering is REALLY IMPORTANT! Since Oklahoma is experiencing drought conditions, it is particularly important this season. Choose a day when the ground is not frozen and the temps are a bit higher, try to make sure trees have about 10 inches of water per month though February. Newly planted trees don’t have a root system that’s well established enough to reach the water that is deep in the soil during winter. . Water trees’ roots adequately before the ground freezes in October and through mid-November. During a mild winter, you will still want to provide some moisture, particularly if you’re seeing any browning on evergreens.
Pruning The dormant season, or the few months of winter when trees grow much slower, is a great time to prune. This practice removes dead, damaged, or dying branches that can steal energy from spring growth and does so at a time that reduces the chances for spreading disease.
Pruning in the winter is a great option for elm trees to help limit the spread of Dutch elm disease, which we have observed a resurgence locally. We have also seen this disease infect trees that were traditionally considered resistant such as lacebark elm and Siberian elm.
Mulching. Mulch acts as an insulator to keep soil temperatures higher, which is one way to keep trees warm in the winter. It also helps prevent cold air from penetrating the root zone of newly planted trees to reduce fall root growth or kill newly formed roots. Place a 3 to 4-inch layer of mulch around the tree’s base, spreading it out at least 2 feet from the trunk, but extending several feet is better for the root system. Remember not to let the mulch touch the trunk.
Since in OK we can't rely on snow to insulate the roots of our trees through the winter, making mulch even more important!
Wrapping. Newly planted or young trees, as well as trees with thinner bark, can benefit from a little winter tree protection in the form of a tree wrap. This is because of the possibility of sunscald, which is when the sun heats up the bark for a short period of time, but then leaves it cracked and dry when the cold temperatures return.
Evergreen needles can suffer as well, soaking up sunlight and then immediately drying out. Wrapping trees in winter can help. But which trees you wrap and how you wrap them varies based on tree type.
Root Damage Due to Salt (Salting Driveways, sidewalks, etc) Try to avoid putting salt somewhere it will run off or be splashed into the root system or body of plants.
If you spread salt, choose one with calcium chloride, or better yet calcium magnesium acetate, which is less harmful to plants than salt composed of sodium chloride.
Rinse trees with ample fresh water when the snow clears to rinse away salt on the trunk.
Irrigate the soil around the tree thoroughly with an inch of fresh water at a time each week for the first two to three months of spring to flush out any remaining excessive salt.
To prepare for salt impacts ahead of time, biochar and compost can also be incorporated into the soil to help with salt resilience.