If your pecan tree harvest is declining, and you have not changed your maintenance habits, you might be dealing with an old tree that is just slowing down.
You can rejuvenate old pecan trees and get them to produce by interrupting the alternate-bearing process. This is done through proper maintenance, such as fertilizing correctly, sticking to a watering schedule, and managing common diseases. Extensive pruning, if done correctly, can also revive an old tree.
Pecan trees will start producing at different ages, depending on whether they were grafted or not. Grafted trees tend to produce earlier, starting at around 5 years old. Native trees can take anywhere from 10-15 years to begin production.
Once the production begins, trees can produce a crop every year, although some years will be lighter than others. This cycle of heavy production followed by light production is called alternate bearing (source).
Pecan trees can live for over 100 years, with some reaching over 300 years old. Some trees will produce good harvests well into their old age, but most begin declining after 50-60 years of age.
If you aren’t sure how old your tree is, you can roughly gauge the age of a tree by multiplying the diameter of the trunk in inches by the growth factor (how much it grows per year in inches).
If your tree is over 50 years old, consider the following rejuvenating tips.
Rejuvenating Old Pecan Trees
Rejuvenating old pecan trees is a process that takes time, effort, and a lot of love. To revive your aging pecan tree, take a look at the following recommendations.
It is normal for pecan trees to go through periods of alternate bearing. This is partly due to the tree’s life cycle. Pecan trees:
- Produce their harvest in the fall, which does not give the tree much time to save nutrients (particularly carbohydrates) before winter.
- Require large amounts of carbohydrates to produce the fats in the pecan nut.
This combination of draining the tree of carbohydrates and giving it a little amount of time to make up for that loss will naturally cause years of lighter harvests.
This is a natural cycle, even if the tree is healthy. However, the older a tree gets, the more prominent this cycle becomes. You can interrupt alternate bearing with good fertilization techniques.
The key to fertilizing pecan trees is balance. Over-fertilized trees will have softer limbs and fruits and untimely production (source), while under-fertilized trees will produce poor yields and become susceptible to pests and diseases.
Two of the most important nutrients for pecan tree production are zinc and nitrogen. Both encourage leaf growth, which directly impacts nut production. It takes about 10 leaf compounds (gatherings of multiple leaves) to support one nut.
The best technique is to do a soil and leaf analysis to determine their nutritional makeup and to supplement accordingly. If that is not possible, apply “complete” fertilizer (like 12-12-12, or 10-10-10).
If you decide to apply nitrogen and/or zinc-specific fertilizers, consult NMSU’s fertilization suggestions for application guidance.
Apply the fertilizer in mid-March. In mature trees, apply another round in the late summer if the crop is heavy, as those nutrients will need to be replaced for the next year.
To determine the amount, measure the width of the tree trunk in inches 4 feet from the ground. For each inch of width, spread 4 pounds of fertilizer but do not use more than 25 pounds. Start a few feet away from the trunk and move towards the edge of the branches (source).
Years of neglect can compound and speed up the aging process in pecan trees. Reintroducing proper maintenance can jolt a tree back into production. Since pecan trees need a lot of water, you may need to modify your irrigation schedule.
Over the years, inadequate watering will cause stunted roots, and they will not be able to reach water from the subsoil. The tree will stay small and the nuts will be small and hard. Overall, this could cut a tree’s lifespan short.
Good watering habits can be hard for homeowners, because at the peak nut production stage a tree may need up to 350 gallons a day. Some of this will come from the soil. However, if insufficient watering habits continue, it can induce alternate bearing.
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Depending on the soil type, your tree will need anywhere from 2”-6” of water 1-2 times a week. Sandy soil may need more water more frequently since it drains quickly. Loamy soils will need closer to 3” of water a week, and hard soils may need less because they do not drain well.
Water should soak in up to 3 feet deep from the trunk to the drip line (the edge of the branches). Sprinklers will not provide enough water to maintain both your lawn and the tree. Use soaking treatments, like soaker or drip hoses (link to Amazon), evenly spaced underneath the canopy of the tree reaching from the trunk to the drip line. Start deep watering in March and continue through October.
Nuts fulfill their sizing stage (physical enlargement) from May to August; inadequate watering at this point will result in smaller nuts. Watering is also essential in the first few weeks of September when nuts reach the filling stage (August through October).
Newer pecan tree varieties are resistant to certain pests and diseases, especially common ones. Old trees do not have this modified protection, so you will need to actively manage disease threats.
The most prominent disease in pecan trees is pecan scab, especially in older trees that cannot naturally resist the disease’s mutations.
Fusicladium effusum, the responsible fungi, can lay dormant in foliage over the winter and grow in early spring rains. The fungi can spread when old foliage and nuts are not cleared from beneath trees before the winter and when trees are poorly ventilated. Infected trees can potentially lose an entire crop (source).
To help prevent pecan scab, remove fallen leaves and debris from around the tree just before winter. Create airflow through the tree by keeping branches cut back and thinned; the airflow will dry out potential breeding grounds for the fungi.
Rejuvenation pruning for old trees includes controversial techniques. Older advice suggests cutting back major portions of the tree at one time, but this may stunt growth. Pruning is effective, but only if it’s done correctly.
Proper pruning should happen in smaller chunks. Remove dead and diseased branches annually, along with overcrowded branches. Thin these out enough to let enough sunlight reach the center of the tree.
Do not “de-horn” your tree. This technique, also known as pollarding, involves cutting each branch at the same point each year to permanently stunt the tree. This weakens the tree over time and will only produce suckers and water sprouts.
Instead, plan a long-term pruning schedule that spans over at least 3 years. Remove a few major branches each year when the tree is dormant, but do not cut them all the way back to the trunk. Leave a small stub, as this will reduce the risk of wood rot.
Starting Pecan Trees
You can enjoy a lifetime of abundant pecan harvests if you plant a tree correctly the first time. Make sure you plant trees in rich, loamy soil to provide nutrition and adequate water retention.
Space trees appropriately so they have ample room to grow. Finally, make sure you plant enough trees to cross-pollinate to ensure heavy nut production.
Space and Soil Conditions
Trees need space for a large root system. Plant your new tree at least 40 feet away from other trees so they do not compete for water and nutrients. Keep them a similar distance away from buildings as well.
Pecan trees can survive in different types of soil, but the soil must be able to drain. Loamy soils are ideal, but sandy soils will work if you can replace the quick drainage with frequent irrigation and apply compost each spring. Hard soils are least conducive, as they will waterlog the roots.
Pecan trees are monoecious, meaning they produce both male and female flowers. If a tree’s male flowers are ready first, the tree is Type I (male). If the female flower is ready first, the tree is Type II (female).
Since the flowers are not typically ready at the same time on the same tree, a second tree is usually needed. They need to be ready at coordinating times (male flowers on one tree are ready at the same time female flowers are ready on the other).
Consult your local extension office to see which trees coordinate well in your area. Plant them within 150 feet of each other, but not less than 40 feet.
Old pecan trees’ crops will eventually slow down, but you can rejuvenate them with a few simple steps. Proper maintenance and pruning techniques can bring an old tree back to life. If you plan on starting trees, starting with these techniques can keep the tree producing for longer.