Methods and Effects of Subordina

Methods and Effects of Subordination Pruning on Young Trees

(preliminary results after one year)

Rob Farrell

VA Dept. of Forestry

P.O. Box 606

Gloucester, VA 23061

(804) 693-2880

rob.farrell@dof.virginia.gov

Joseph Murray

Blue Ridge Community College

P.O. Box 80

Weyers Cave, VA 24486

(540) 453-2349

murrayj@brcc.edu

Results and images @ www1.brcc.edu/murray/research/subordination

Purpose:

To measure the effectiveness of reduction pruning v. thinning to influence branch aspect ratio.

Subordination pruning has been recommended as a method to alter the growth of branches to improve tree structure and branch union strength. Subordination pruning is intended to slow the growth of the branch so that the branch aspect ratio is reduced and the main trunk of the tree can maintain apical control. However, few guidelines are available for subordination pruning and there is an absence of controlled studies evaluating the effectiveness of various subordinate pruning methods.

This study is evaluating two methods of subordination pruning (reduction pruning and thinning) in their ability to influence growth rate and branch aspect ratio.

Methods

Two sites:

Weyers Cave, Virginia: 20 white oak trees, eight years old, planted equidistantly apart in a field with full exposure to sun.

Charlottesville, Virginia: 8 northern red oak trees, ____ years old, planted equidistantly in a landscaped area a commercial office park with full exposure to sun.

Additional sites will be selected in Virginia. Trees will be selected to represent common landscape species. Where possible, trees of similar age and condition will be used to allow for comparisons between pruning methods and controls.

Trees that are selected for inclusion into the study are randomly assigned to one of the treatment/control groups (Weyers Cave: length reduction by 25%, length reduction by 50%, thinning by 50%, or control; Charlottesville: length reduction by 50% or control)

Measurements include;

DBH (or caliper)
Height of the tree
Annual growth of the trunk (main stem)
For each tree, three branches are selected for detailed measurements with only one of the three branches being pruned on the trees selected for a pruning method.
- diameter of the trunk at the branch bark ridge and 2 cm above the branch bark ridge,
- branch diameter at the branch bark ridge and the branch diameter 2 cm away from the branch bark ridge,
- annual growth of the representative branches

Pruning and measurements will be conducted during the dormant season.