Green Horizons

Think of crop tree release as crown thinning, or thinning from above. This practice focuses one’s effort on the best trees in the stand. It pays more attention to managing tree canopies. So, just what are crop trees?

Crop tree release is thinning from above, or focusing on management of tree canopies. The goal is to maximize space around each crop tree.

Crop trees are trees that produce, or have the potential to produce, the desired landowner benefits. If, for example, improved deer or turkey habitat is desired, a large-crowned white oak tree that produces abundant acorns would be a valuable crop tree. If increased economic value is an important ownership objective, a 14"-diameter black walnut tree with a straight, defect-free trunk and healthy crown would be a valuable crop tree.

Since the focus is on maximizing growing space around each crop tree, it can result in a pretty heavy cut. From a personal aesthetics point of view, if you want your woodland to have a dense forest look and feel, then releasing all of your crop trees may result in an unacceptable visual effect. If that is the case, release fewer crop trees. It is far more desirable to completely release fewer crop trees than to partially release more. Research has shown that partially released trees grow at a much slower rate than completely released trees. In just a few short years the crop tree crowns will expand and lessen any negative visual effect and you can completely release another group of adjacent crop trees. Because the intensity of this practice depends upon your objectives, and realizing that no two woodlands are the same, you might want to initially seek the help of your forester.

For example, if you own 10 acres and intend only to release three or four hard mast-producing trees per acre to improve wildlife habitat, you may need to do little more than walk over the property and select trees based on the selection criteria and their spacing throughout the woodland. On the other hand, if you own 50 acres and wish to release 20 to 30 crop trees per acre to favor timber production and wildlife habitat, you may need a fairly detailed inventory to determine the number of suitable crop trees, identify their location, evaluate their potential to respond to release, and indicate how many trees need to be removed to release those crop trees. Also, if the trees to be removed are merchantable and the removal is to be a commercial sale, some form of formal inventory will be desirable for marketing purposes. Now you definitely need the assistance of a trained and experienced professional.

It is often a good idea the first time you perform a crop tree release to visually identify your crop trees and trees to be removed by placing a ribbon around the trunk of the trees. For example, you could use blue flagging for your crop trees and red flagging for the trees to be removed or deadened. Evaluating the visual impact before cutting will allow for adjustments if the anticipated results are not desired. The old carpenter’s rule, "measure twice, cut once" is a good rule to follow, especially in the forest!

Trees to be removed are those individuals whose crowns touch the sides of, or overtop, the crowns of the crop trees. Trees whose crowns are below those of the crop trees’ crowns do not provide significant competition and are usually not removed or deadened. Ideally, a crop tree should be released from competing crowns on all four sides of its crown.

Occasionally, two crop trees will be close enough to each other that both trees cannot be released on four sides. It’s okay to keep both trees. Simply release the other three non-competing sides. In general, younger stands will require more crop trees to be released since not all crop trees will survive until the stand matures. In the winter issue of Green Horizons, we will talk about ways to remove your unwanted trees.