MASTER GARDENERS: Fall care and pruning those shrubs and trees
This is a fall we can probably put down in the record books—no frost until almost the second week of October, fall rain instead of spring rain, and very cool summer nights. How did your tomatoes do?
Since we have a long mild fall, take some time to look at your trees and shrubs and to plan for the pruning you need to do now and later.
Most trees should be pruned in the late dormant season, before spring growth starts. Now is the best time to mark dead branches and limbs you plan to prune to improve shape on landscape trees. After the snow gets deep, it is easy to forget what they looked like in summer. Dead limbs may be pruned now. When you prune, make sure you leave the collar so the wound closes up; do not prune flush to the trunk.
The exceptions to late winter pruning are any trees that bleed readily. This includes birch, maple, boxelder, walnut, and ironwood (hornbeam). Wait until they are fully leafed out in late spring or early summer. Mark the limbs to prune with plastic marking ribbon or tie bright yarn around the limb.
Shrubs and trees that are grown for their blooms are best pruned after they finish blooming because they set buds for next year soon after they bloom. These include lilac, forsythia, flowering plum, cherries, azalea, chokeberry (aronia), Juneberry, and flowering almond. This is a good time, however to look at their shape, size, and presence of old wood so they may be pruned later.
Blueberries and other spring fruit bearing plants have already set their buds for next spring so pruning now will reduce your spring crop. Limit your pruning to dead wood, witches broom, and diseased canes.
Now is a good time to inspect your fruit trees and other trees with thin bark for evidence of black rot or stem cankers that present as discolored sunken areas on the trunk and branches. Check chokecherry and other members of that family for black knot, prune it out and burn it if possible. If you have mountain ash, spruce, birch, or maple—check for sapsucker damage. This looks like evenly spaced rows of small holes that can girdle a tree if severe or serve as a route for some other infection.
Most evergreens can be pruned any time but late spring is better. This is the time to protect your sensitive evergreens that have open southern exposure from late season sun scald. Wrap with burlap or shade by other means.
Many trees and shrubs are lost from rodent and rabbit damage in the winter. Protect thin barked trees and shrubs by making a cylinder of hardware cloth to go around the trunk and at least 2 feet tall. Close the cylinder with zip ties so they can be removed in the summer to allow grass and weed removal. It also helps to remove all grass and vegetation from the base of trees and shrubs before freeze-up.
Time spent now will make your spring work easier and leave more time to page through those seed catalogs!
Check the Yard and Garden section of the University of Minnesota website—www.extension.umn.edu/garden/yardgarden/—for more information on fall horticulture topics.
Need help? Call (218) 444-7916; leave your name, number, and question and a Master Gardener will contact you.