Charles Graham, Coolman, Denise | 4/26/2005 8:28:45 PM
SHREVEPORT – An LSU AgCenter researcher says trimming pecan trees could make owners more money in the long run.
Dr. Charles Graham, a researcher at the LSU AgCenter’s Pecan Research Station near Shreveport, said he and other researchers are completing the third year of a tree-trimming project at the station. The trimming – dubbed "hedging" – involves cutting back limbs that are less than 1 ½" in diameter along the outer canopy of the pecan trees in an orchard.
"Pecan trees planted at 35 to 40 feet spacings generally begin to crowd about 10 to12 years after they have been planted," Graham said. "When this happens, growers can remove entire trees or hedge their trees to give the trees more room."
Once the trees start crowding, Graham said, the lower canopy of the orchard becomes excessively shaded. This is detrimental to the trees.
"Too much shade causes the lower limbs to die out," he said. "When the lower limbs die out, growers lose production in the lower parts of the trees, and the nuts are only produced in the upper canopy where the sunlight is."
Cutting back pecan trees is a maintenance tool that researchers believe should be used more often. If growers wait too long and have to remove limbs that are larger than 1½ inches in diameter, the tree may go into a vegetative state with limited nut production.
"Pecan trees tend to replace wood that has been cut off as quickly as possible," Graham said. "Often growers wait too long to hedge their trees. They have to cut large limbs, which leads to compensatory growth of the canopy. Hedging keeps trees smaller, and smaller trees are easier to manage."
Trimming the trees also opens the canopy of an orchard and improves sunlight penetration.
"As pecan trees get larger, the ratio of foliage to nuts becomes less and less," Graham said. "This causes a reduction in nut quality and often leads to alternate bearing problems. Young trees don’t have this problem, because they have a better ratio of nuts to foliage. Large trees, however, don’t have this ratio and should be hedged or have the crop mechanically thinned to improve the ratio."
Machines needed to do this type trimming are similar to a tractor with saw blades mounted on an arm. The machine is driven through an orchard, and the saw blades are used to cut back the limbs.
Commercial hedgers generally charge between $100 and $200 per hour, according to Graham, who says other costs such as transportation of the equipment to the orchard and orchard cleanup also may be involved.
A new hedging system recently was purchased for use at the LSU AgCenter’s Pecan Research Station. This system uses a sickle-type bar, similar to the ones used to cut hay. It runs about $20,000 compared to more than $100,000 for the large commercial machines.
"Most hedging equipment in the past has been too expensive for small orchard owners to buy," Graham said. "But prices are coming down. Now, they have equipment that can be attached to a tractor. For instance, the sickle bar we use works great on small limbs. If a grower follows a hedging schedule, the sickle bar works great."
For the best results, trim just before the trees begin to touch, Graham said.
"If growers will stick to a hedging schedule, they can delay removal of trees from their orchards," he said. "Growers should coordinate hedging operations with periodic tree removal to maintain high nut quality and maximize production of the orchard."
The cycle used by LSU AgCenter researchers calls for trimming two sides one year and then the other two sides two years later. More research needs to be done to develop information on hedging cycles that maximize production, Graham said.
Decisions to hedge, or trim trees, should be made before an orchard is planted, according to Graham, who said plans for this management technique should be made early.
"Hedging is something that needs to be planned for," he said. "Growers need to start maintaining their orchards before there is a problem. They don’t need to wait until there’s a crowding or shading problem and then use hedging as a last-ditch effort. An orchard can’t be resurrected by hedging alone."
Trimming pecan trees as a maintenance tool began during the 1970s, experts say, pointing out that successful hedging is a long-term project that is done to reduce shading and maintain tree size. If the trees have already begun alternate bearing cycles, growers are advised to make the first initial hedge just before an on-year for the orchard.
"Pecan orchards have alternate bearing cycles," Graham said. "One year will be a good year and then the next year will be an off-year. Producers pretty much know what year is an on-year and what year is an off-year for their orchards. If hedging is done during an off-year, the production will be even less than it would’ve been if hedging hadn’t been done."
According to the 2003 Louisiana Summary of Agriculture and Natural Resources produced by the LSU AgCenter, more than 28,000 acres are planted to pecan orchards in the state, and the gross farm value for pecans in Louisiana last year was more than $15 million.
For more information on pecans or a variety of other topics ranging from production agriculture to family and home life, visit www.lsuagcenter.com.