By Adam Austing & Katie Drewitz, University of MN Extension educators
As March welcomes us with mild weather perhaps you are looking for something to do to get out of the house. There are a few tasks you can be focusing on to help get you ready for spring, including pruning your trees. An old rule of thumb was to prune in winter while the plant was dormant. For best results, we need to be a bit more specific than that, but it’s a start. When to prune depends on the species, but for most, late-winter into early-spring is the best time to prune.
Pruning near the end of the dormant season has several advantages, including: 1) Limited time remaining before the tree or shrub will begin its spring growth and healing process. 2) Avoid certain diseases and pests. 3) Provides easier sight and access without deciduous foliage.
Oak wilt can be a devastating disease and continues to spread throughout Minnesota and therefore oak trees should not be pruned during the months of April through mid-July. If an oak tree is damaged or wounded during this time period, it is best to cover the wound surface with a water-based paint or pruning sealer to help minimize the attraction of pests that may spread the disease.
Fruit trees such as apples, crabapples, mountain ash, and hawthorns should be pruned in February through early April. This reduces the chance of the bacterial disease fire blight and infection from occurring. Pruning in fall or early winter may cause drying out and die-back at the pruning sites.
Trees with sap will “bleed” during late-winter or early-spring pruning. Although it may look alarming this does not cause harm to the tree. One option with these types of trees or shrubs such as maples, boxelders, birch, and walnut or butternut, is to prune them after their leaves are fully developed in late spring or early summer. However, never remove more than one-quarter of the live foliage.
Early spring blooming trees and shrubs such as forsythia, flowering plum, lilac, azalea, chokeberry, chokecherry, and flowering crab should not be pruned in the late winter or early spring. Instead, these early bloomers should be pruned after they have finished blooming. If they are pruned at any other time, once the flower buds are set, you will be pruning off next spring’s flowers.
Remember that late winter and early spring is the best time to prune many of your trees and shrubs. Do your research, have the proper tools, and be careful. For more information on pruning visit www.extension.umn.edu and search for pruning. You can also contact your local Extension Office. Residents of Wright County can email firstname.lastname@example.org or call (320) 249-5929.