Horticulture: June 2002 Other Horticulture Articles

The differences between growing native and improved pecan varieties are still causing confusion among growers. Native pecan growers often comment, "I'd rather not have any of those improved pecans in my orchard. They just aren't worth anything." On the other side of the controversy, improved pecan growers say, "There is no room for a native pecan tree on my place. They take up room where improved pecans could be grown." In reality, there is a place for both native and improved pecan production, although not necessarily intermingled.

A flood irrigated orchard A native orchard

The reason for the controversy is that improved varieties require greater inputs than do native varieties. Native pecan trees have evolved in the locations where they have grown for centuries. If allowed to perpetuate themselves, the descendants will continue to dominate that site for centuries to come. Because of the selection process in the wild, the genetics that perform the best will dominate. Often, heavy-yielding trees give rise to trees that aren't as productive.

Native pecans have a tremendously diverse gene pool. Dr. L.J. Grauke, research horticulturist with the USDA's Agricultural Research Service, has looked at some of the genetic diversity across very different growing regions. He found that when seeds were collected from those regions and planted on the same site, they exhibited different characteristics. In one instance, he found that wild populations developed on alkaline soils had the ability to take up zinc from the soil much better than those populations developed on more acidic soils. We must remember that these populations of native trees have evolved on those sites since creation.

On the other hand, improved varieties that have been selected for their desirable traits have no natural selection or genetic diversity. Sure, there are advantages to having a Choctaw or Pawnee orchard, but with that come quirks of the variety. Whatever the problem is, it must be dealt with — or the owner will be disappointed in the outcome.

If you will, liken the native pecan to a wild horse that has adapted to harsh environments and needs little care. Contrast that with a purebred racehorse, which is likened to improved pecans. Does a caretaker turn a well-bred racehorse out on native grass and expect it to be ready to win the next Kentucky Derby? No! He feeds and trains a correctly bred horse, doing whatever it takes to prepare the horse to be a winner.

When improved pecans are introduced to an area, the manager should understand the quirks of that variety, and be prepared to provide the necessary inputs that enable the variety to perform to its genetic potential. For instance, Mohawk is probably the most intensive variety that has been planted in Oklahoma. It is one of those love/hate varieties. It requires 40 to 50 additional inches of irrigation water over natural rainfall, 150 to 200 pounds of actual nitrogen per year plus possible potassium fertilization, at least four foliar zinc applications, annual green pecan thinning by shaking in August, and, as the trees get older, annual pruning to keep parts of the tree vegetative. Varieties such as Mohawk are so difficult to grow that they should be avoided if the grower can't give them all the inputs needed for intense pecan culture.

Does this mean that we should not grow improved pecans in Oklahoma? No! It means that when thinking about planting a new pecan orchard, one should investigate the varieties and learn all they can about them. If the grower is limited on inputs into the pecan operation, he should consider a smaller-sized nut variety that exhibits scab resistance, has smaller yield capability, and is very hardy — a variety such as Kanza. On the other hand, if the grower is able to irrigate and wants to grow higher yields of high-value nuts, he may want to consider Pawnee.

Be careful when introducing pecan varieties into an environment different than that in which they were selected. The USDA Pecan Breeding Station at Brownwood, Texas, where Dr. Tommy Thompson and his predecessors selected varieties for release, is equipped with irrigation. Most other sites where the pecans are tested are also irrigated or on great soil types, often with sub-irrigation. The Kanza variety was identified and encouraged for release by Dr. Mike Smith at Oklahoma State University and Dr. Bill Reid at Kansas State University because they noticed how well it performed under adverse conditions with no irrigation.

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