Timely and Effective Winter Tree Pruning

By CHAD P. GIBLIN Trees & Me LLC

Pruning young trees is really about proactive tree preservation. When the proper pruning dose is applied at the ideal time, care is directed at creating a mature form that is structurally sound and able to resist branch failures during wind, snow, and ice loading events. When trees are smaller than eight inches pruning should focus on the transition from frequent nursery pruning schedules to those that are much less frequent in the landscape. The challenge lies in developing a functional mature crown while maintaining an attractive young form. In many cases a compromise in aesthetics is required to establish a strong canopy.

Proper pruning dose is the volume of canopy that can safely be removed during a single pruning event. Dose is calculated using several factors including tree establishment status, growth rate, inherent resistance to decay, and the time between pruning cycles. A dose that is too low or too high can have equally negative effects on the developing crown in a young tree.

half the size of the stem where they are attached until permanent removal. This will minimize the wound size when they are thinned at the main stem and promote quicker wound closure. The exact size of the pruning cut will vary depending on the tree species and its growth rate as well as resistance to decay.

The first step in pruning young trees is to identify a strong central leader. Next, the height of the lowest permanent scaffold branch should be established; this may be variable depending on the species and location. Trees located in public boulevards may require higher permanent canopy than those located in parks or on private property. Branches below permanent canopy are considered temporary and will need to be pruned to a smaller lateral branch to reduce or suppress their growth and eventually thinned at the main stem. All temporary branches need to be managed to keep them less than one-

When approaching medium sized trees ranging from 8 to 12 inches in diameter, pruning cuts should be kept relatively small and in the outer periphery of the canopy. As trees approach maturity their growth rates level off and some species may respond poorly to large pruning cuts, especially when made on the main stem. Knowing tree species profiles and their ability to resist decay is critical in making these decisions. In many cases, if a large branch doesn’t need to be removed for clearance it can simply be reduced to direct resources to higher, more central portions of the canopy.

Larger trees really need to be assessed for structural defects that create risk due to targets below. These defects may include decay, branch inclusions, and codominant leaders as well as branch unions that are actively failing. The goal is to prevent or mitigate the effects of failure. Much like the approach with medium-sized trees, pruning cuts should focus on the outer canopy to reduce the sail on weak or defective branches. This can reduce the lever action on poorly attached unions and prevent failure during loading events. Cabling can be used to reduce the load on these unions as well.