A detailed explanation of walnut grafting techniques, a must-learn method for growing walnuts

Since 1997, Dingzhou Desheng Company has carried out a large number of applied experiments on top grafting for variety improvement of large walnut trees and budding for seedling propagation, and through many years of production practice has formed a complete grafting technical system; the survival rate of top grafting for crown replacement on large trees and the survival rate of budding on seedlings both reached above 90%.

Scion collection: vigorous, well-developed shoots with small pith, free of pests and diseases, and a diameter of 1.0-1.5 cm should be selected as scions. Scions can be collected from the time the walnut leaves fall until just before bud break.

Scion storage: top grafting is carried out around mid to late April, so the scion storage period is relatively long. To prevent the buds on the scions from rotting or sprouting, the optimum storage temperature for scions is 0-5 degrees C.

Wax sealing of scions: the paraffin temperature should be controlled at 105-115 degrees C, so that the wax coating on the scions does not easily fall off during grafting.

Rootstock tree selection: the age of the rootstock tree used for top grafting should be less than 20 years, and the tree is required to be vigorous, with a smooth grafting site and a junction diameter of 3-8 cm.

Grafting period: the best period for top grafting is from bud break of the rootstock tree to the leaf expansion stage.

Rootstock tree treatment: 4-5 days before top grafting, saw off the branch heads and make bleeding cuts at the base of the trunk as planned, to reduce the effect of sap flow on the survival rate.

Grafting method: bark insertion and tongue grafting, with the graft union tightly bound and sealed with plastic film strips.

Water control after grafting: no irrigation is allowed within two weeks after top grafting, and water accumulation at the graft union should be dealt with promptly.

Removing sprouts after grafting: sprouts on the rootstock tree should be removed promptly after grafting to prevent nutrient consumption and help the graft union heal.

Grafting period: the best period for walnut budding is from May 20 to June 20.

Scion collection: select vigorous developed shoots as scions. After cutting the scions, immediately remove the leaves, keeping only 1.5-2.0 cm of the petiole, and cover them with wet burlap sacks to prevent water loss.

Scion storage: use immediately after collection. If short-term storage is needed, bundle the scions and stand them upright in a container with clean water, with a soaking depth of about 10 cm, cover the top with wet burlap sacks, place in a cool place, and change the water 2-3 times a day; they can be kept for 2-3 days.

Cutting the bud piece: make a horizontal cut 0.5 cm above the bud and 0.5 cm below the base of the petiole, each deep enough to reach the xylem (cutting only the phloem), then make a vertical cut on each side of the base of the petiole, extending to the two horizontal cuts, and remove the square bud piece for later use.

Cutting the rootstock: on a smooth part of the rootstock 15 cm above the ground, cut an opening the same length as the bud piece and about 1.2-1.5 cm wide, then make another vertical cut on the outer side; the depth of these cuts is required to cut only the phloem without damaging the xylem. Then pry open the rootstock bark from the side cut, and after prying it open, tear off a 0.6-0.8 cm wide strip of rootstock bark.

Inserting the bud piece: fit the cut bud piece into the square opening in the rootstock.

Tying the bud: tie from bottom to top, wrapping tightly.

Cutting the rootstock: cut or bend the rootstock, leaving 2 compound leaves above the grafted bud. About 10 days after grafting, when the petiole of the grafted bud can fall off, or when a small number of grafted buds begin to sprout, cut the rootstock 1.5-2.0 cm above the grafted bud. When the shoot grows to 10 cm, remove the plastic tying strip.