Determining the gender of a mulberry tree can be challenging until it starts producing flowers. Male mulberry trees typically produce long, cylindrical catkins that hang down from the branches. Female mulberry trees produce shorter, rounder catkins that are more compact. Once the tree starts flowering, you can easily identify its gender by observing the shape and size of the catkins. Keep in mind that some mulberry trees are self-fertile and can produce both male and female flowers on the same tree.