O.S. Gray, Waxahachie, Texas
Pruning and shaping has become a regular practice with the older domesticated fruits, such as the peach and apple, but has just come into prominence with pecans and other nuts.
The Pruning of a Pecan Tree
The shape of a tree is highly important. To have the proper frame-work means as much to a tree as having the proper foundation means to a building. While this is a new subject and the speaker does not care to attempt to give any hard and fast rules, it is felt that ideas can be given that will prove sound until something better is developed, should future experience prove a change necessary or desirable.
The development of the proper type of framework for a tree has much to do with its ability to withstand heavy storms, increases its ability to stand up under the strain of heavy crops, may increase the available bearing surface, and will be of invaluable assistance in making easier such operations as harvesting and spraying of pecan trees.
Central Leader Pecan Tree Type
Where the terminal bud of a vigorous tree is not interfered with, a tree of the “central leader” type, as shown in figure 1, is normally developed. Pine and sycamore trees furnish excellent examples of this type of tree. If the top of a tree is properly cut back at the time of transplanting, the upper lateral bud usually develops into a leader of the pecan tree.
The principal advantage of the central leader type is its great strength that enables the pecan tree to withstand severe storms and to bear up enormous weights. A distinct disadvantage is that the tree usually reaches such a height as to make spraying and harvesting difficult.
Open Vase Pecan Tree, or "V" Type
In case of injury (including pruning) to the terminal bud of a leader, oftentimes the lower lateral buds get a vigorous start, take all the strength of the tree, and as a result the central leader is started out. This usually results in a distinct type of tree best explained by figure 2, known as the open vase, or “V” type. This style is usually recommended for each tree.
The condemning feature of the open vase tree for pecans is the fact that the crotches make a very weak tree. Hundreds of trees in older nut orchards have broken under the strain of wind and crop, and expensive bracing with chains and rods has been necessary. My observation of young trees in Texas pecan orchards teaches me that Texas growers are allowing hundreds of trees of this type to develop in growing pecan orchards. A few judicious clips with the pruner or strokes of the pocket knife will easily remedy the trouble while the trees are young.
Figure 4 shows a young orchard developing into open vase type in orchard of a prominent Texas pecan man. Notice weak crotch developing. This tree could have been easily trained a few years ago, but now most of the top will evidently have to be removed in order to form a strong framework.
Modified Leader Pecan Tree
My own personal choice of types is a combination of both the central leader and the open vase trees, and is known as the “modified leader” tree. It seems possible to combine in a large way the good points of both extreme types with a mini-mum of their disadvantages.
In this type there is a pronounced central leader through the first four to ten feet of the main frame, which then divides into a strong, compact, spreading top. This type is obtained by maintaining the leader for the first four or five years, or longer if necessary, and then cutting it back to a strong lateral branch fifteen feet or less from the ground.
A tree of this type is illustrated in figure 3. This tree may well serve as a model for training pecan trees and is one of the most beautiful and symmetrical trees that the writer has seen. It has a spread of over sixty feet; its framework is well built and strong, and its upper branches can be reached with a good power sprayer.
When a pecan tree reaches the proper height for heading, usually four to six feet from the ground, the grower should be careful not to leave over two or three lateral limbs; otherwise they may take the entire strength of the tree and choke out the leader. Even with this precaution, it is often necessary to check the growth of some laterals by careful pruning or by judiciously “pinching” off terminal buds from the limbs to be checked.
Briefly, then, our ideal tree will branch from four to six feet from the ground; then the lateral limbs constituting the main framework will be well distributed up and down the next four to ten feet of central trunk, which then divides into a spreading top.
Fix Your Ideal Type in Mind
While I feel safe in saying that the modified leader is the type we want beyond any doubt, you will have observed that I have not attempted to give you definite measurements. These measurements will vary according to the ideas of various individual growers. The thing that I want to urge our growers to do is to make a study of this problem, observe strong, typical native pecan trees and note their strong and weak points; then decide what you want and work to that end.
The shaping of your tree is not easy. Ravages of bud worms often give much trouble to the orchardist. Certain varieties have certain characteristics of growth that must be taken into consideration. Certain varieties are naturally upright in growth, while others are naturally spreading. We are going to have more experience with varieties, however, before venturing any suggestions along this particular line.
Those who are working over native groves can profit greatly by studying tree shapes and types. You can often have your choice between trees with strong frames and trees that are weak. It is often possible, in top-working to completely change the framework characteristics by judiciously cutting back.