This cycle of heavy production followed by light production is called a reciprocating bearing (source). Walnut trees can live for more than 100 years, and some can reach more than 300 years. Some trees produce good yields well into old age, but most begin to decline after 50 to 60 years of age. According to the Missouri Botanical Garden, a pecan tree can take eight to 10 years to produce a crop.
Even after this period, lack of pecans is sometimes normal. The University of Georgia explains that walnut trees are alternate in size, which means that it is common for them to produce a bountiful harvest one year and a negligible harvest the following year. Pecans have particular requirements for pollination, nutrients, and pest control if they are going to produce bountiful crops. Remember that many pecan cultivars don't start producing nuts until they're between 12 and 15 years old.
Inadequate lime or fertilizer: Lack of lime, nitrogen fertilizer, and zinc are common limiting factors in pecan production. Fertilize according to soil and leaf sample recommendations. For many years, lack of pollination causes the greatest loss of nuts. Since pecans are only pollinated by wind, excessive rainfall during spring bloom prevents pollination, as noted above, and poorly pollinated flowers produce small nuts that later abort.
Insect pest damage, disease pressure and drought are three other factors that can cause premature fruit fall. Alternative production in pecan production means that a tree produces a relatively abundant harvest of nuts one year and a lighter one the next. It is characteristic of walnut and other hardwood forest trees. To reduce the effects of alternative production, choose cultivars that tend to be consistent annual carriers and then practice good orchard management.
Healthy trees of any variety are better able to produce pecans on a consistent basis from year to year. You may have a variety of walnut that produces little. Do you know if they are all the same variety of trees? Also keep in mind that walnut trees that are grown from seedlings generally do not produce nuts for 10 years. However, pecan trees grown from grafted rootstocks are generally produced in about four to eight years.
While pecan trees can produce a crop each year once they start, they produce large yields of nuts every other year. The phenomenon, called alternate bearing, means that trees produce light crops in the other years. The most common solution to compensate for this is to plant two different cultivars where the pollen spilled from one tree coincides with the receptivity time of the female flowers on the other tree, and vice versa. The extent to which nut production will be affected will depend on both the severity and duration of extreme temperatures.
Alternative production is believed to be an adaptive response to reducing pest pressure by not allowing a constant supply of nuts, for which pests can thrive. For example, a variety like Schely rarely yields a good harvest when the trees are not sprayed because the trees are extremely susceptible to walnut scab, a fungal disease. Without a soil test, the general rule of thumb for fertilizing pecan trees is one pound of 13-13-13 fertilizer per tree for each year of the tree's age, up to 25 pounds. Fumigation may not be a viable option for growers with only a few trees, but proper sanitary control can help control pests.
With pecans, pollination is the first step needed for nut production, and this is mainly facilitated by the wind; pollinating insects are not really a contributing factor. Trees should be at least forty feet apart to provide enough space for future growth, good air circulation, and exposure to light. Poor pollination: A single isolated pecan tree will generally not pollinate effectively, as most varieties shed pollen too soon or too late to pollinate the female flowers of the same tree. There's usually no single reason why a pecan tree won't produce a crop or produce poor quality nuts.
Aphids, pecan weevils, and American walnut shell worms are among some of the insects that can limit production. Pecans are wind-pollinated, so trees need to be planted relatively close to ensure proper pollination. When trees produce a large crop of nuts, there are not enough nutrients for that year's nuts to ripen and for the tree to store enough plant food for proper production in the following year. For a tree to grow vigorously enough in the spring to produce the leaves and flowers it needs for a good harvest, it must carry enough food reserves assimilated during the winter to support its first growth spurt.
Choose well-drained soil, provide drainage for excess water, and keep trees watered during dry periods. . .
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