By Nathan Winter
Extension Educator, McLeod and Meeker Counties
The spring time weather will soon be heading our way with April only weeks away. The winter period has been the time for meetings and the spring brings outdoor activities and scratching of the soil for planting. From recent phone calls in the McLeod and Meeker County Extension Offices, I can tell people in the community are thinking ahead to spring. They are wondering what they should plant and how soon they can start? Often, many of the common questions revolve around tree management. For example, when should I prune my apple trees? Well, if you have not already, there is still some time for certain species of trees.
Prune apple trees, including flowering crabapples, mountain ash, hawthorns and shrub cotoneasters in late winter from February to early April. Spring or summer pruning increases chances for infection and spread of the bacterial disease fireblight. Autumn or early winter pruning is more likely to result in drying and die-back at pruning sites. Oaks, ash, and elm trees can also be pruned this time of year.
Pruning approaches include crown thinning, crown raising, and crown reduction. Crown thinning is primarily used in hardwoods to increase the amount of room for light and air to penetrate the tree. You still will want to maintain the trees natural shape, and form.
Another form of crown thinning is to make sure there is only one dominant leader instead of two or more co-dominate leaders on the tree. Crown raising is cutting off some of the bottom branches to permit travel underneath the tree. This could be for lawn mowers, people, and vehicles. Be sure not to raise the crown of the tree too high to avoid an excessively high crown.
Crown reduction is another approach to pruning. This method should be used only in a last resort when the tree has outgrown its permitted space. This approach should not be used on trees with a pyramidal growth form.
Topping and tipping pruning practices do more harm to trees than they help. Topping is pruning large upright branches between the nodes and is sometimes done to reduce the height of the tree. Tipping is pruning lateral branches between nodes to reduce the crown width. These practices result in sprouts and dead branches that will reduce the life of the tree. Use the crown reduction method as a last resort and avoid topping and tipping.
What about treating the wounds? Most of the time the tree sap, gums, and resins naturally work to decrease pathogens invading the trees. Therefore, there are very few circumstances when wound dressings are needed for pruning cuts. Often, they create more problems than they avoid.
The University of Minnesota Extension Website contains a vast amount of information. The website has further information pertaining to pruning other types of trees. Following is a great link to learn more about pruning trees and shrubs: http://www.extension.umn.edu/distribution/horticulture/dg0628.html.