Ask the ISU Extension Garden Experts About: Pruning Trees

Pruning equipment

What type of equipment do I need to prune trees and shrubs? 

Proper pruning tools for a home gardener include hand shears, lopping shears and a pruning saw. 

Hand or pruning shears are generally used for cutting stems (branches) up to 3/4 inch in diameter. There are two basic types of hand shears. Scissor-type shears have curved blades that overlap (scissor action) when making the cut. Anvil-type shears have a sharp top blade that cuts against a flat surface (anvil). Scissor-type shears are generally preferred as they can make closer cuts and are less likely to crush stems. 

Branches from 3/4 to 1 1/2 inches in diameter can be effectively cut with lopping shears. Lopping shears consist of two blades attached to long handles. The long handles give the gardener greater leverage so cuts can be made through larger branches. Lopping shears are also excellent for pruning difficult to reach places.

Use a pruning saw on branches larger than 1 1/2 inches in diameter. Various types of pruning saws are available. A pole saw can be used to prune hard-to-reach branches in trees. 

Pruning cuts

Where should I make the final cut when pruning a tree branch? 

When pruning trees, make the final cut just beyond the branch collar and branch bark ridge. The branch collar is the swollen area at the base of the branch. The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk. Pruning just beyond the branch collar and branch bark ridge retains the tree’s natural wound defense mechanisms and promotes compartmentalization and callus formation.

Avoid flush cuts when pruning trees. Flush cuts are pruning cuts made as close as possible to the trunk or main branch. Flush cuts produce larger wounds than cuts made just below the branch collar. They also destroy the tree’s natural process of walling off or compartmentalizing wounds. 

Large branch pruning

What is the proper way to prune a large tree branch? 

To prevent extensive bark damage, use a three-cut procedure when pruning branches that are greater than 1 1/2 inches in diameter. Make the first cut 6 to 12 inches from the main branch or trunk. Cut upward and go about one-third of the way through the branch. Make the second cut 1 to 2 inches beyond the first. As the second cut is made, the weight of the branch will cause it to break at the pivot point between the two cuts (the initial, bottom cut prevents the branch from ripping off a large piece of bark as it breaks). Make the final cut just beyond the branch collar and branch bark ridge. 

Sap from pruning cut

Sap is flowing from a pruning cut on my maple tree. Should I be concerned? 

Some tree species, such as maple, birch and elm, “bleed” heavily when pruned in late winter or early spring. However, the loss of sap does not harm the trees. The trees will not “bleed” to death. Eventually the flow of sap will slow and stop. 

Painting pruning wounds

Should I paint the pruning wounds on my trees? 

Do not apply a pruning paint or wound dressing to pruning wounds. The application of a pruning paint or wound dressing does not prevent wood decay and may actually interfere with the tree’s natural wound responses. Oak trees are an exception to the no paint recommendation. To prevent the transmission of oak wilt, oak trees should not be pruned in spring and summer. If an oak tree needs to be pruned during the growing season, for example to correct storm damage, immediately (within 15 minutes) paint the pruning cuts with a latex house paint. Winter (December, January and February) is the best time to prune oak trees in Iowa. There is no need to paint the pruning wounds when oaks are pruned in winter. 
[PHOTO] Final cut of three-cut procedure is made  just beyond the branch collar and branch bark ridge.