How to Choose Seedling Varieties When Establishing a Walnut Orchard

  1. Variety types and pollinizer configuration. Varieties are the foundation of high-quality, high-yield fruit trees. Variety selection is a key step in walnut development. If varieties are chosen appropriately, the goals of high yield, high quality and high benefit can be achieved; otherwise, losses can be great due to low fruit set rate or varieties that are unsuitable or not matched to the site. The selected varieties must have undergone a certain period of cultivation trials locally to prove whether they are superior varieties.

  At present, walnut varieties that have passed national or provincial appraisal or approval fall into two types: early-bearing and late-bearing. Early-bearing walnut varieties generally bear early and have strong high-yield potential, but they have strict requirements for cultivation conditions. If the site conditions are poor and management cannot keep up, with no fertilizer application and no pruning, they are prone to premature aging after 4~5 years of bearing and may even die. Therefore, early-bearing walnut varieties are best developed in places with good site conditions; in places with poor site conditions and extensive management, late-bearing walnut varieties should be chosen.

  Walnuts have characteristics such as dichogamy, wind pollination, short pollination distance and relatively large differences in fruit set rate. In order to create good pollination conditions, suitable pollinizer varieties should be selected. When establishing an orchard, 3~4 main cultivars should generally be selected according to the female and male flowering periods of the walnut varieties. If there are large seedling trees within 50 m of the field edges and ridges, 2~3 trees may be appropriately retained, and pollination need not be considered when establishing the orchard, because large seedling trees have many flowers, large differences between upper and lower parts, and a relatively long male flower pollen-shedding period, which can generally ensure pollination needs.

  In principle, the ratio of main cultivars to pollinizer varieties is 6~8 : 1. The maximum distance between main cultivars and pollinizer varieties should be less than 100 m. When planting on flat land, 1~2 rows of pollinizer varieties can be configured for every 4~5 rows of main cultivars, while on mountain land and terraced fields this can be handled flexibly according to the above principles, ensuring that the full bloom period of the pollinizer varieties is consistent with that of the main cultivars, and that the nut quality of the pollinizer varieties is also excellent.

  2. Seedling preparation. The quality of seedlings not only affects the survival rate at orchard establishment, but also relates to how early or late they bear fruit later, the level of yield, and the economic benefits of orchard establishment. Therefore, quality control for seedlings must be strict. The standards for high-quality seedlings are: well-developed main root, complete lateral roots, no pests or diseases, strong branching ability, plump branches and full buds. When using superior seedlings, variety verification, registration and labeling should be carried out before planting, and any errors should be corrected promptly to avoid variety mixing and planting confusion; seedlings should also be quality-checked and graded. Qualified seedlings should have an intact, robust root system, thick branches with short internodes, plump buds, bright bark color, be free of quarantine pests and diseases, and meet national standards. It is best to use 2~3-year-old vigorous seedlings, with a height of more than 1 m, a trunk diameter of not less than 1 cm, and many fibrous roots. Substandard, poor-quality weak seedlings, diseased seedlings and deformed seedlings should be strictly rejected or eliminated. Seedlings that have been transported over long distances have lost more water, so the packaging should be opened immediately and the roots soaked for one day and one night; after the seedlings have fully absorbed water, they can be planted or heeled in. They can also be soaked in ABT rooting powder solution for 3 hours before planting, which will greatly increase the planting survival rate.

  If the orchard area is large, the practice of raising seedlings locally and planting them locally should be promoted in production. If seedlings need to be purchased from elsewhere, protection should be strengthened to prevent wind and sun from causing seedling dehydration, ensure the safe transport of seedlings, and take care that varieties are not mixed.