The decline in nut production from mature pecan trees is often the result of accumulated neglect and management deficiencies, not simply age. When mature trees cease to produce quality nuts, it indicates their physiological needs are not being met. Restoring consistent productivity requires a multi-faceted approach focusing on the tree’s internal health and external environment. Addressing nutritional imbalances, poor canopy structure, and external stressors like water availability and pest pressure can return these old trees to good production.
Revitalizing Soil Health and Nutrient Uptake
Pecans have a high demand for specific nutrients, and deficiencies are a primary cause of low yield in older trees. The micronutrient Zinc (Zn) is important for nut production, playing a direct role in the expansion of new foliage and the setting of fruit. Since zinc is often unavailable to pecan roots in soils with a pH of 7.0 or higher, the most effective application method is a foliar spray directly onto the leaves. This bypasses the soil’s chemistry, ensuring the nutrient is absorbed by the developing foliage.
Foliar zinc applications should begin early in the spring at bud break. Continue treatments on a schedule of three to five applications at two to three-week intervals during the flush of new growth. A common mixture uses two to three pounds of 36% zinc sulfate per 100 gallons of water, aiming for thorough coverage of the new leaves. While soil application is an option for trees in acidic soils (pH below 6.0), the foliar method is preferred for quick uptake.
Mature pecan trees have a substantial need for Nitrogen (N), which fuels the vegetative growth required to support a heavy nut crop. Annual nitrogen application rates for bearing mature trees range from 150 to 250 pounds of actual nitrogen per acre. This fertilizer should be broadcast evenly across the area beneath the canopy, extending from the trunk out to the drip line where the active feeder roots are concentrated.
Optimal nitrogen delivery involves splitting the total annual amount into two applications: one around bud break in early spring (March or April) and a second in late spring to early summer (May or June). This split application ensures a steady supply of nitrogen to support initial leaf expansion and subsequent nut sizing. While nitrogen and zinc are the most frequently required nutrients, a soil test should be conducted every few years to determine the need for Phosphorus (P) and Potassium (K), which are less commonly deficient.
Structural Pruning for Canopy Renewal
Over many decades, an old pecan tree’s canopy becomes thick and dense, causing significant self-shading that limits nut production. New fruiting wood is created on the current season’s growth and requires ample sunlight, which the crowded interior cannot provide. This lack of light leads to the death of internal branches and shifts production to the outer canopy edge, reducing overall yield.
Restorative pruning focuses on “thinning out” the canopy rather than “heading back” or indiscriminately cutting off branch tips. The goal is to selectively remove branches to create light wells and improve air circulation, allowing sunlight to penetrate the lower and inner parts of the tree. This work involves systematically removing dead, diseased, or crossing limbs that rub against each other.
Structural intervention involves removing crowded secondary branches, particularly those growing straight up or inward, to open the canopy. Pruning should be performed during the dormant season, ideally in late winter or early spring (January through March), before the tree breaks bud. This timing minimizes stress and promotes vigorous growth in the spring.
If the tree is excessively tall, selective removal of upper limbs can safely lower the canopy’s height, making future management like spraying and harvesting more feasible. However, this restorative pruning should be spread out over several seasons. Removing too much canopy at once can stress the tree and trigger an undesirable flush of non-fruiting water sprouts. Gradually thinning the canopy ensures the tree adapts and redirects energy toward forming healthy, productive fruiting wood.
Managing Environmental Stressors
Consistent water availability influences the quality and retention of a pecan crop, especially in older, large-canopy trees. Pecan nuts require an uninterrupted supply of water during the nut sizing period (late spring until mid-August) and the subsequent kernel filling stage (through early October). Drought stress during these times causes the tree to shed nuts prematurely (“June drop”) or results in poorly filled kernels.
During the peak nut filling stage, which is most intense in the first two weeks of September, a mature tree can demand hundreds of gallons of water per day. Irrigation should be deep and thorough, wetting the soil to a depth of three to four feet beneath the entire canopy area, not just near the trunk. This deep watering ensures the extensive root system has access to moisture.
A variety of pests and diseases can significantly reduce yield by damaging the nuts or defoliating the tree. Pecan scab, a fungal disease, is a major concern, causing black lesions on leaves and nut shucks that can lead to total crop loss. Pests like the pecan weevil pose a late-season threat, with the female laying eggs inside the developing nut, resulting in a wormy kernel.
Management of these biological threats begins with good sanitation, such as removing old leaves and husks from the ground where pests and diseases can overwinter. Regular monitoring for pests and early signs of disease is necessary. However, spraying mature pecan trees requires specialized high-pressure equipment that most homeowners do not possess. For severe or persistent issues, consulting a certified arborist or professional spray service is often the most practical course of action.