Pecan Tree Crowding
Among the most painful experiences for a pecan grower is the dreaded task of cutting down a mature tree. Research and experience has repeatedly shown that as crowding occurs and competition among trees increases, the production of nuts decline. The only solution in most cases is to remove excess trees. The resolve a grower must muster to remove excess trees is akin to the traditional expression, "biting the bullet". To minimize the trauma, we usually recommend that the owner first make complete arrangements for proper removal of the excess trees and take a vacation (be gone) during the operation.
Over 45 years ago, Professor Herman Hinrichs, horticulture researcher at Oklahoma State University determined that 30 square feet of cross-sectional trunk area per acre was the appropriate pecan tree spacing for optimum nut production. Today, his work is the model used throughout the US pecan belt to determine when to remove excess trees. For practical use, 30 square feet of trunk area per acre is the approximate equivalent of leaving 10-20 feet distance between the branch tips of adjoining trees. Thus when limbs of adjoining trees touch or worse yet 'lap', crowding is severe and nut production potential is reduced significantly.
Another 'down-to-earth' rule that is useful in determining proper tree spacing is to remove trees until no more than 60 percent shade covers the orchard floor during the middle of the growing season at the same time of day that Tex Ritter sang about (12 o'clock high noon).
Figure 1 shows a crowded pecan orchard that was declining in nut production. Figure 2 is a view of the orchard after excess trees were removed. Increased annual nut production can be expected from this orchard after two to four years if recommended management practices including fertilization, reduction of grass/weed competition and control of insects and diseases are followed.
Pecan tree crowding often slips up on us much like 'sin'. The trees continue to make relatively small, insignificant amounts of growth each year. The tree crowding is so gradual that it is not strikingly noticeable to a person that is in the orchard regularly. In fact, we're often not aware of crowding until we suddenly realize it has 'got us' - by then significant nut production is already lost.
When pecan trees are properly managed, crowding is occurring continuously and thus periodic removal of excess trees is an ongoing chore. Perhaps we should organize a support group for pecan tree owners so they can come together, share their innermost feelings regarding their loss of trees, receive consolation and gain strength from each other. May you always enjoy new hopes and old memories.