The mulberry is the edible fruit of the Morus genus, a group of deciduous trees belonging to the fig family, Moraceae. These trees have a widespread distribution, growing naturally or under cultivation across temperate, subtropical, and tropical climates globally. Historically, the mulberry has been highly significant, most notably as the exclusive food source for the silkworm, an association that fueled the ancient silk industry. The tree is also valued for its attractive leaves and its fruit, which have been consumed and used in folk medicine for centuries.
The Fruit’s Appearance
The mulberry fruit is not a true berry but is structurally classified as an aggregate fruit, similar to a blackberry. This means the mature fruit is composed of many small, fleshy drupelets clustered tightly around a central core. A fully ripened mulberry is typically small and elongated, often measuring between three-quarters of an inch to an inch and a quarter in length. The texture of the ripe fruit is soft, succulent, and very juicy, making it highly perishable and difficult to transport without bruising. Mulberry fruits display a wide range of colors when mature, including white, pink, red, and dark purple to black. The color of the fruit alone is not a reliable way to identify the species, as some varieties of White Mulberry (Morus alba) can produce dark-colored fruit.
Identifying the Tree by its Leaves
Identifying a mulberry tree often relies heavily on examining its leaves, which are known for their high degree of variability, even on the same branch. The leaves are arranged alternately along the stem and feature a serrated or toothed edge. This means the leaf margin is not smooth but has small, sharp projections. A single tree can produce leaves that are unlobed, mitten-shaped (one-lobed), or deeply three- to five-lobed. Younger trees or vigorous shoots often exhibit a higher proportion of deeply lobed leaves compared to the more entire, unlobed leaves found on mature growth. Red Mulberry (Morus rubra) leaves tend to be larger, thicker, and rougher on the upper surface than White Mulberry leaves.
Tree Structure
The bark of the mature mulberry tree is generally rough or furrowed, contributing to the tree’s sturdy, deciduous appearance. Depending on the species, the tree can reach heights ranging from a small, shrubby size of around 30 feet to a larger stature of up to 70 feet. The white mulberry was traditionally grown for silkworms, while the black mulberry is often favored for its fruit.
Key Differences Between Common Species
The three most widely known species are the White Mulberry (Morus alba), the Red Mulberry (Morus rubra), and the Black Mulberry (Morus nigra), each originating from a different part of the world. M. alba is native to China and was cultivated for silk production, leading to its aggressive introduction and establishment in North America, where it is often considered an invasive species. This species is typically a smaller tree and its fruit is often described as blandly sweet, though it can range in color from white to black.
The native North American species, M. rubra, is found in the eastern United States and is the largest of the three, capable of reaching heights of over 60 feet. Its fruit ripens to a dark red or nearly black color and is generally sweeter and more flavorful than the white mulberry.
Black Mulberry (M. nigra) originates from western Asia, specifically the region of Iran and Mesopotamia. Morus nigra is widely regarded as producing the largest and most flavorful fruit, characterized by a balanced sweetness and tartness. The fruit of the Black Mulberry is notable for having a very short stem, in contrast to the more noticeable stems found on the fruits of M. alba and M. rubra. This species tends to be a smaller, slower-growing tree, reaching a maximum height of about 33 feet, which makes it easier to harvest.