When should pecan trees be planted, and how many years until they bear fruit?
The pecan (Carya illinoinensis) is native to the Mississippi River basin region of the United States and was introduced to China in the early 20th century. It belongs to the family Juglandaceae, the genus Carya, and the species Carya illinoinensis. Compared with China's native hickory (Carya cathayensis), whose nuts are small with thick shells, red kernels and an astringent taste that requires boiling in water to remove the astringency before use and consumption, the pecan's fruit is elongated-ovate or elliptical, with large nuts, extremely thin shells, a smooth surface, plump kernels rich in oil and aroma, an oil content generally above 70%, and a sweet taste with excellent quality; it can be eaten raw, roasted, or made into pastries, and is delicious, making it a world-famous nut. The pecan is also a high-quality timber species. The cultivation method for nut production is introduced below.
When should pecan trees be planted? How many years until they bear fruit?
Site selection: Planting is best suited to areas with an average annual temperature of 9-16°C or above and annual rainfall of more than 800 mm. Because it is a deep-rooted fruit tree with relatively weak drought resistance, soil that is deep, fertile and has strong water retention is more suitable. Walnuts are light-loving fruit trees and require ample sunlight, so when establishing an orchard on mountainous land, south-facing slopes are preferable.
Planting grafted seedlings: Grafted seedlings can bear fruit 4-5 years after planting and enter the full-production period in 8-10 years, while seedling-raised trees need 8-10 years to bear fruit and about 15 years to enter the full-production period. Therefore, pecans grown for nut production must use grafted seedlings. Generally, planting in September-November is best. Under the premise of controlling the crown and shoots to dwarf the tree, a row spacing of 5 m × 4 m or 5 m × 5 m can be used. The pecan is a monoecious tree with separate male and female flowers, and the female and male flowers on the same plant generally do not bloom at the same time, so cross-pollination between different plants is required. Therefore, only orchards planted in blocks can achieve high yields. Dig holes with a diameter and depth of 1.5 m each, then apply base fertilizer (40 kg organic fertilizer, 500 g superphosphate, 20 g aldrin powder) and mix thoroughly with the soil before planting. After planting, water thoroughly to settle the roots, and cover the tree disc with weeds to help survival.
Training and pruning: Carry this out during the dormant period from winter to early spring. In the year of planting, do not prune at all; only straighten the trunk and protect the terminal bud. After bud break in spring, the terminal bud grows upright and is used as the central leader. About 2 years after planting, begin pruning and training: when the seedling is about 2 m tall, pinch out the top shoot and select 3-4 evenly distributed, vigorously growing side branches as the first tier of main branches, then select the second and third tiers of main branches; retain 2-3 main branches in the second tier, 60-80 cm from the first tier, and retain 1-2 main branches in the third tier, 50-70 cm from the first tier. Since the pecan mainly bears fruit on vigorous branches, side-growing vigorous branches must be used as scaffold branches, and the inner canopy must be kept well ventilated and exposed to light.
Strengthen management: For young trees, apply light fertilizer frequently; from the year of planting until after bud break, begin topdressing once a month, and apply base fertilizer by the end of September. In years 2-4, apply fertilizer 4 times a year in March, June, August and October. For mature trees, apply base fertilizer in September-October, with 5000 kg fully decomposed organic fertilizer, 50 kg phosphate fertilizer, 100 kg plant ash and 15 kg urea per mu. Apply topdressing once before bud break the following year and once in June-July. Also pay attention to the control of powdery mildew, brown spot, black spot, scab, aphids, jewel beetles and slug moths.