Step One: Pruning and Cutting
When it comes to large trees that need to be replaced with better varieties, the shape of the tree should be carefully planned based on its current condition. Big branches are arranged in a structured way, while unnecessary ones at the base are removed. The remaining branches are cut to stimulate latent buds to sprout, and both permanent extension buds and temporary spare buds are selected according to the tree's growth potential.
It is best to perform this pruning before the start of the growing season, as this reduces sap flow and helps promote the germination of latent buds, as well as speeds up wound healing. The number of branches to be cut should not be excessive. For medium-sized trees, the first layer should be above the main branch, with the central leader cut back to about 60 cm. The first layer of primary branches should be pruned to around 50 cm. For tall trees, the second layer should be above the main branch, with the central leader cut back to 30 cm, the second layer of main branches pruned to 20 cm, and the first layer of main branches to 50 cm. All cuts should be flattened and covered with a plastic film to prevent cracking and encourage faster healing.
After cutting the trunk, it’s important to select the right buds for future growth. This means choosing the center bud on the upper left side of the trunk, the second layer leaving a main branch extension shoot tip, and a lateral spare bud. On the main branches of the first layer, leave an extension shoot tip and one lateral bud on each side. In areas where there are no existing branches, it's essential to leave some empty buds. Any unnecessary buds should be removed promptly to reduce nutrient consumption. The selected extension buds and alternate buds should be trimmed to about 20 cm for grafting purposes.
Step Two: Grafting
Choose high-quality walnut varieties suitable for your region and perform grafting in the year following the pruning or in June of the next year. Grafting techniques vary—skilled individuals can use block budding, while others may prefer I-shaped budding. A double-edged knife made from two pieces of thin wood is ideal for creating rectangular blocks (3 cm wide and 2 cm thick), ensuring a clean and precise cut. No matter which method you choose, make sure the graft interface is aligned correctly, with the cut surface matching the bud. After grafting, wrap the area tightly with a transparent film wider than the interface to ensure a secure seal and improve survival rates.
Once the graft is complete, proper care is essential. If grafting takes place in July, it’s important to prevent the buds from sprouting prematurely. After grafting, only the grafts should be removed; other branches and leaves should remain untouched. Do not cut the scion or remove the bandage until spring when the buds begin to grow. Wrap the film securely. For grafting done in June of the following year, focus on controlling the growth of the new shoots so they can survive the winter. After grafting, leave three compound leaves and cut the scion after 10 days. Check the graft’s survival, remove any extra buds, and concentrate nutrients to support the growth of the graft. When the graft has grown about 10 cm, carefully cut the stem and release the film to promote rapid growth. By late August, prune the top and control the lower growth. Additionally, although walnuts have strong healing abilities, the graft requires more leaf coverage than other fruit trees. Therefore, the graft should still be tied to a stick to prevent wind damage.
Step Three: Positioning and Shaping
By the third year of the renewal process, the new grafts are typically about 80 cm long, and the Weibei dryland walnut cultivation technique begins. It’s crucial to position and shape the tree properly to restore the canopy quickly. Here’s how to do it: after the leaves appear in spring, leave healthy upright extension branches in the center and shorten them to 80 cm. Promote the second or third layer of main branches and pull the other branches horizontally to serve as auxiliary support branches. Shorten the second layer of the trunk to 60 cm to encourage the development of the second side branch. Don’t cut or trim the lateral branches. If the extension branch is damaged, replace it with a nearby spare branch. The rest of the temporary buds should be gradually released to produce early results. In summer, you can adjust the direction of the main branches using techniques like bending or tying.
In the following summer, continue adjusting the azimuth angle of the main side branches. Select the second or third layer of the main branch on the central branch and thin out the remaining branches from the base. Gently release the extended branches of each layer and cut the lateral branches at full buds to encourage branching. Temporary spare branches that help with ventilation and light should be removed, but those that don’t interfere with the main branches can be kept. At this stage, the basic structure of the new tree is complete. Over the next few years, continue adjusting angles, removing useless branches, and controlling back branches. Allow all branches to grow naturally. The temporary spare branches will eventually be removed to avoid interfering with the main branches’ growth.
Experience has shown that this three-step approach not only rejuvenates old trees and improves their variety but also rationally modifies irregular shapes. Using this method, trees such as walnuts and others have achieved their first fruiting within three years and reached peak production in five or six years, doubling their original yield. (Gansu Science and Technology News – Ma Haisheng)
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