Walnut trees are medium-sized trees that grow walnuts--used in recipes and eaten as a snack. Walnuts trees usually take more than 10 years to become fully mature. There are three different ways to propagate walnut trees. Each of these propagation methods have different drawbacks and benefits.
The purpose of propagation is to increase the stock of walnut trees. Most walnut farmers continually try to increase stock to ensure that they continue to produce the most walnuts and the most healthy and disease-resistant plants. Continual reproduction and propagation ensures that the trees never die out completely, and the walnut farmer is able to continually improve his walnut crop by finding the best propagation method for the kind of walnut.
There are three different methods that walnut trees can propagate through. Branch grafts enable farmers to cut branches from more mature and healthy trees and graft them on younger, less productive trees. Bark grafts produce a similar result, but instead of cutting a branch and grafting it to the tree, a whole section of bark with a small branch attached is cut to graft to another tree. Typically, these grafts are made on older trees. Walnut trees can also be propagated by planting the walnuts themselves. This method does not produce as many walnuts as quickly as the other methods, but it does allow new host trees to continually grow in case other trees die.
The main benefit of propagation through branch grafting is the ability to have large crops of walnuts much sooner. The farmer cuts branches from the healthiest, most productive tree and grafts them to trees that produce less nuts. With branch grafting, all trees are top performers. Bark grafting is a safer method of grafting than branch grafting. The branch is more secure against the tree, and the tree is less susceptible to disease along the branch cut. The benefit of planting walnut seeds is that there is a greater likelihood of the propagation lasting for many years.
Branch and bark grafting are asexual propagation. It does not require pollination. Walnut trees are not capable of asexual reproduction on their own, but asexual reproduction can occur when employed by a skilled gardener or farmer. Asexual reproduction is when one tree is cut and forced to join or make another completely different tree. Sexual reproduction is done by seeding. The flowers must be pollinated by insects or birds, which then produce the walnuts that fall and get planted. Sexual reproduction requires two walnut trees to achieve.
Commercial farms typically employ all of the propagation methods on their farms. Grafting is done to boost nut production, while seeding is done to form new trees that will have grafting in the future. A multitiered propagation plan helps farms continually produce consistent, healthy crops.