The mulberry plant, belonging to the genus Morus, is a deciduous species widely known for its edible fruit and its historical role in sericulture, or silk production. While often referred to colloquially as a “bush,” the mulberry is typically a small to medium-sized tree, depending on the species and pruning habits. Identifying a mulberry relies on recognizing a few distinct physical characteristics, as the genus exhibits high variability in its features.
General Structure and Growth Habit
Mulberry trees generally display a rapid growth rate when young, maturing into medium-sized trees that can reach heights of up to 24 meters. Many are smaller and more shrub-like in cultivation or as saplings. The tree often develops a short, somewhat crooked trunk, which supports a rounded or widely spreading canopy of branches. The overall form tends to be irregular, especially in older specimens.
The bark of a mulberry is relatively thin and ranges in color from light brown to a grayish hue. On mature trees, the bark texture can be highly variable, appearing smooth with shallow furrows or developing long, narrow, and sometimes ridged sections. When the bark is damaged, a milky latex sap, characteristic of the Moraceae family, may be visible beneath the surface.
The Defining Feature: Mulberry Leaves
The most distinctive and often confusing feature of the mulberry is the extreme variability in its leaves, a trait known as polymorphism. A single tree, or even a single branch, can display leaves of entirely different shapes. These leaves are simple, alternately arranged along the stem, and have serrated or toothed edges.
While some leaves are unlobed and heart-shaped or oval, others are deeply divided into two, three, or even five lobes. The two- or three-lobed leaves often take on a distinct “mitten” shape, which is particularly common on younger growth or fast-growing shoots. Leaves on older, more stable wood tend to be less lobed and more uniformly heart-shaped.
The texture of the leaf surface also provides an important clue for identification between species. The upper surface can range from smooth and glossy to noticeably rough or hairy, a detail often used to separate the various Morus types. Despite the shape differences, the alternate arrangement and fine serrations remain consistent across all leaf types on the same plant.
Flowers and Fruit Appearance
Mulberry plants produce small, inconspicuous flowers that lack petals and appear in dense, elongated clusters called catkins. These catkins are typically greenish and emerge in the spring from the leaf axils of the current season’s growth. The trees can be either dioecious, meaning male and female flowers are on separate plants, or monoecious, with both sexes on the same plant.
The fruit of the mulberry is a multiple fruit, or aggregate fruit, which develops from the entire flower cluster. It physically resembles an elongated blackberry, made up of many small, fleshy drupelets fused around a central core. The fruit is relatively small, generally measuring between two and three centimeters in length.
The color of the ripe fruit is highly misleading, as the common names do not reliably indicate the berry color. Fruit can ripen to white, pink, red, or deep purplish-black, depending on the individual tree and species. The fruit generally matures over a period from mid-spring to late summer, ripening gradually and often staining surfaces below the tree when it drops.
Distinguishing Common Mulberry Types
The three most common mulberry species are the Red Mulberry (Morus rubra), the White Mulberry (Morus alba), and the Black Mulberry (Morus nigra), and they are distinguished by a combination of traits.
Red Mulberry
The Red Mulberry (Morus rubra) is native to eastern North America and tends to be the largest, reaching up to 21 meters in moist, mature forests. Its bark is grayish with scaly, flattened ridges, and its leaves are characteristically rough and dull, with fine pubescence covering the underside veins. The native Red Mulberry fruit ripens to a dark purplish-black and offers a balanced sweet and tart flavor.
White Mulberry
The White Mulberry (Morus alba), originally from Asia, is often invasive in North America and found in disturbed or urban areas, as it is relatively shade-intolerant. Its leaves are generally smoother, glossier, and less hairy than the red mulberry. Its bark is tannish-brown with thick, braiding ridges, often exposing a yellowish inner layer. The White Mulberry fruit color is the most variable, ranging from white to red or deep black, and the flavor is often described as bland or simply sweet.
Black Mulberry
The Black Mulberry (Morus nigra), native to Southwest Asia, is prized for having the largest and most flavorful fruit. This fruit is juicy and distinctly sweet and tart.