I've been browsing online, looking at several nurseries that sell nut trees and seeds. One practice that seems to be quite common is to graft Walnut trees onto Black Walnut rootstock. This is done for both Butternut trees and Persian Walnut trees. It's made me curious. Why is this done? Black Walnut trees are pretty aggressive growers. Their roots go down real deep, real fast. Is this the reason? Does it make the tree more resistant to more infections? Also, does this mean the tree emits Juglone like a 100% Black Walnut tree? Or does it emit lesser amounts like, say, the Butternut that is grafted on to it?
