The fruitless mulberry tree is a cultivated variety of the White Mulberry, Morus alba, specifically selected because it does not produce fruit. These trees are typically male clones grown for their excellent shade-casting properties. Female mulberry trees produce abundant, staining fruit that creates maintenance issues on walkways and patios. Identifying a fruitless specimen requires evaluating its physical structure, its variable foliage, and the type of reproductive structures it produces in the spring.
General Appearance and Growth Habit
The fruitless mulberry is known for its rapid growth rate, quickly developing into a substantial shade tree. It generally reaches a mature height of 20 to 50 feet with a comparable spread, forming a dense, rounded canopy.
The trunk bark provides an identification clue visible year-round. On mature trees, the bark is grayish-brown and develops shallow vertical furrows and irregular ridges. Younger twigs may show an orange-brown color. The tree also tends to develop a shallow, branching root system that is sometimes visible at the soil surface.
Distinctive Leaf Characteristics
The foliage is the mulberry tree’s most distinctive visual feature, confirming the tree is Morus alba. The leaves are arranged alternately on the stem, are simple, and have a serrated margin. Their texture is typically glossy and smooth on the upper surface, with a light to medium green coloration.
A defining botanical trait is heterophylly, meaning highly variable leaf shapes appear on the same tree. Shapes range from unlobed, simple ovate leaves to deeply lobed forms that resemble mittens or have three to seven distinct lobes. This variation is pronounced on younger shoots.
Mature leaves measure between four and eight inches long. Hairs on the underside are usually sparse and confined mainly to the junctions of the major veins. This combination of variable shape and glossy texture is a reliable indicator of the White Mulberry species.
Confirming Fruitlessness: Reproductive Structures
The final and most conclusive step is confirming the tree’s male gender, as all truly fruitless mulberries are male clones. Mulberry trees are dioecious, meaning male and female flowers grow on separate plants. Fruitless varieties are propagated exclusively from male trees.
In the spring, the male tree produces small, inconspicuous, yellowish-green catkins. These staminate catkins are narrow, cylindrical structures, typically one to two inches long, that hang pendulously. They contain only stamens, the pollen-producing organs, and lack the pistil required to develop into a berry.
These male catkins release their pollen, dry up, and drop cleanly. Confirmation of fruitlessness occurs in late spring or early summer, when female trees would be developing berries. The complete absence of developing fruit, dried remnants, or dark stains beneath the canopy proves the tree is a sterile, male cultivar.