8 to 10 meters. Grafted Wenwan walnut trees can grow to 8 to 10 meters. Wenwan walnut trees are tall trees. Seedlings are generally only one or two meters long. Adult trees can grow to about 5 meters in five years. The older the tree, the taller the trunk. , some can even grow to 8 meters or even 10 meters, so an iron frame is needed to facilitate picking walnuts.