What rootstock should be used for grafting walnut trees? Timing and method are key

The walnut tree, also known as the Persian walnut tree and black walnut, belongs to the Juglandaceae family, and its varieties are divided into wild hickory and artificially grafted and improved walnut varieties.So which trees can generally be used to graft walnut trees? When is the right time to graft? How to graft?

Which trees can generally be used to graft walnut trees?

Generally, only plants of the same family and same genus graft well onto each other. The best options for grafting walnut trees are:

1. Grafting onto seedling walnut (seedlings grown from walnut seeds) rootstock.

2. Juglandaceae, genus Juglans mandshurica can be grafted, such as the common Manchurian walnut (hickory), but it is prone to the small-foot phenomenon (thin rootstock, thicker above the graft union).

3. Juglandaceae, genus Pterocarya (southern), can also be used to graft walnut.

When is the right time to graft walnut trees?

1. The suitable time for branch grafting is from early April to early May. Since this technique is not easy to master and the survival rate is not high, this method is not recommended.

2. The best time for bud grafting is from mid-May to late June. At this time the temperature and humidity conditions are suitable, both rootstock and scion grow vigorously, callus tissue forms easily after grafting, the buds grow quickly after sprouting, and the degree of lignification is high, which is conducive to safely overwintering.

How to graft walnut trees?

1. Rootstock treatment: remove overly dense and excess branches and shape the tree form. Select and keep branches with a thickness of more than 1 cm, choose the grafting position within 10 cm from the main branch (to keep the tree form compact), then leave 4-5 leaves above the branch and remove the tip. The direction of the grafted bud is handled flexibly; the direction of the central leader bud faces inward, and the remaining lateral branch buds face one side or the back of the branch, which helps restore the tree form.

2. Bud collection: choose a bud from a scion that is similar in thickness to the rootstock, mature and plump, and use it as the grafted bud. When taking the bud, when about 1 cm above the bud body, cut horizontally back toward the original direction of the cut, then at the opened notch on one side push the bud body forcefully toward the other side, so that the xylem and phloem of the bud plate separate. Make sure the entire growing point is removed, and finally tear off the bud plate by hand.

3. Grafting: on the rootstock to be grafted, choose a smooth part with a suitable position and direction, and make one horizontal cut according to the size of the bud plate. Make a vertical cut (the length must exceed about 2 times the length of the bud, which helps with sap drainage), then make another horizontal cut, tear off the phloem, and the removed part should be about 0.2 cm larger than the length and width of the bud. Then place the prepared bud into the rootstock, making sure that one horizontal and one vertical edge of the bud align with the two sides of the rootstock. Finally, use a plastic strip with good elasticity to tie the bud tightly from bottom to top, ensuring that the cambium of the bud and the rootstock are in close contact, with no places where air can get in.

Management after grafting

1. Removing sprouts, cutting the rootstock, and untying: one week after grafting, the buds of the rootstock begin to sprout. These seedling sprouts should all be removed, keeping the leaves left when the rootstock was cut for photosynthesis, and protecting the bud plate from direct sunlight. Continue removing sprouts until the seedling buds no longer sprout. When the grafted bud grows to 5 cm, or when the grafted bud has healed, cut the rootstock, leaving 3 cm above the grafted bud. When the grafted bud grows to 15-20 cm (when the bud plate has healed), untie it.

2. Fertilizer and water management: after grafting, strengthen fertilizer and water management according to soil moisture conditions. When the soil moisture deficiency is not too serious, do not water or fertilize for 2 weeks after grafting; in case of severe drought, water. When the new shoots grow to more than 10 cm, topdress and water in time. Generally, apply 50 jin of urea per mu, and water once after topdressing. After watering, cultivate and weed in time to prevent excessive water evaporation and weed damage. After July, spray 300-500 times diluted potassium dihydrogen phosphate once every half month to promote branch fullness, prevent excessive seedling growth, and improve overwintering ability.