Extension Educator, Horticulture
A few warm days and gardener's hands start twitching in search of activity and in search of a new layer of spring calluses produced from days spent pruning every tree and shrub within arm length. However we do need a basic understanding of trees and shrubs before we turn into Edward Scissorhands. Proper pruning means knowing when to hold 'em and when to fold 'em.
Proper pruning, along with regular watering, is a vital part of young tree maintenance. How a young tree is pruned can determine how well it stands up to wind and ice as it ages. Pruning is an ongoing process throughout a tree's life involving yearly evaluation and planning. It requires decisions on what to prune, when to prune, and whether to prune at all.
With newly planted trees limit pruning to removal of dead and broken branches and the correction of competing central leaders. Begin training for tree shape 2-3 years after planting.
The popular notion of removing branches solely due to the reduced root system of a newly planted tree is just down right wrong and really doesn't make sense. Branches are the framework for the green leaves required for the plant to make its own food for root and stem growth. Branches are not burdensome parasites sucking the life out of the tree. (Can you tell this is one of my pet peeves?)
Branches contain food reserves and vital hormones. When the growing tips of branches are removed, most plants quickly form new leaves and stems below the cut. This new growth may seem good to us but it is actually at the expense of root growth. With new trees we want to encourage root growth so the plants can get established. If the tree does not have the energy to keep the branches it has due to a reduced root system, it will clearly tell you with branch death.
Sometimes trees will develop competing central leaders that can lead to structural failures. It's important to deal with this problem early in a tree's life. Generally this competition is fairly obvious when two or more central branches are the same size and length. Pick one branch as a dominant then reduce the length or remove competing leaders. This may take a few years of corrective pruning to solve so as not to remove more than one third of the tree at one time.
Another key aspect to pruning young trees involves what we don't prune. Leave lower branches on the tree for the first few years after transplanting. Research has shown that the presence of low branches helps the tree to develop a stronger and larger trunk than if the branches are removed. Lower branches also protect the trunk from sun scald and mechanical injury. Leave the temporary lower branches on the tree as long as possible. Try to keep them at least until they reach one half to one inch in diameter. Some trees due to their location near sidewalks or streets eventually have to be limbed high, but consider leaving lower branches on some landscape trees. You may find you enjoy the appearance and the added branches can help as a windbreak or screen.
Other tips on training young trees:
Stop by our office for the free guide - Under the Canopy: A Guide to Selecting, Planting and Caring for Trees in Illinois.