Mulberry, known botanically as Morus, is a species of flowering and fruiting trees that contains several cultivars. Mulberry trees are commonly dioecious, meaning that they are male or female, and the female-bearing trees require the pollen of the male, non-bearing trees to set fruit. The leaves on the species are medium to large, green and in a shape the looks like a cross between a maple and a fig leaf. The ripe fruit that arrive in summer are red, purple, black or white in hue and resemble blackberries.
According to Virginia Tech, mulberry trees are small, reaching just 60 feet in height at maturity, and possess a short trunk with a low branch line. The difference between the male and female flowers is quite subtle and sometimes difficult to discern, as they bloom at the same time.
Inspect your mulberry tree carefully and often in the late spring from mid-April through May, when both the male and female mulberry flowers, known as catkins, will appear.
Look for pale green, slightly tapered, clustered, hanging catkins between 1 and 2 inches in length, as these are the male catkins. Female catkins are the same color and general form but are shorter, at a maximum of 1 inch in length.
Look for catkins on the trees that have a slimmer, more narrow profile and are longer than the others. Female catkins are not only shorter than the male flowers, but wider in diameter by 1/8 inch to 1/4 inch, making them look plump when compared to the male catkins.
Determine a female mulberry tree by fruits that will appear on the tree in clusters in from spring to late summer, depending on the cultivar. Black mulberries ripen in the summer, while red and white do so in spring. Male trees will have no fruit.