The mulberry tree belongs to the genus Morus and the family Moraceae, which also includes the fig and the breadfruit. These deciduous trees are found growing both wild and under cultivation across many temperate regions, including Asia, North America, and Europe. The genus consists of approximately 10 to 19 species, with the three most commonly recognized types being the white, red, and black mulberries. Known for their rapid growth when young and their sweet, edible fruit, mulberries are widely distributed.
Defining Characteristics of the Genus Morus
Plants within the genus Morus are fast-growing when young, slowing down as they mature, and rarely exceeding 50 feet in height. A defining feature is heterophylly, meaning the leaves on a single tree can vary significantly in shape. Leaves are simple, alternately arranged, and feature serrated edges, often being deeply lobed, especially on younger shoots.
The flowers are generally unisexual, appearing in tight, catkin-like clusters. Trees can be either monoecious (bearing both male and female flowers) or dioecious (bearing only one sex). The fruit is technically a multiple fruit, developing from the entire flower cluster and resembling a blackberry. All mulberry species exude a milky sap, or latex, when a twig or leaf is cut.
Identifying the Main Species (Red, White, and Black)
Identifying a mulberry tree can be challenging because the common names—white, red, and black—refer to the color of the dormant buds, not necessarily the fruit color. The three main species are Morus alba (White Mulberry), Morus rubra (Red Mulberry), and Morus nigra (Black Mulberry), each with distinct origins and traits.
White Mulberry (Morus alba)
The White Mulberry (Morus alba) is native to China. It is the most widespread species, often growing taller and straighter than other types. While its name suggests white fruit, M. alba can produce berries that are white, pink, red, or deep purple. They are generally the sweetest and least acidic of the mulberries.
Red Mulberry (Morus rubra)
The Red Mulberry (Morus rubra) is the only species native to eastern North America, typically growing in moist, wooded areas. This species is the largest of the genus, sometimes reaching heights of 70 feet. Its fruit is always dark purple or black when ripe, offering a sweet and juicy flavor profile, often considered superior to the white mulberry. Red mulberry leaves are generally larger, darker green, and have a rougher texture.
Black Mulberry (Morus nigra)
The Black Mulberry (Morus nigra) is native to southwestern Asia, specifically Persia and the Caucasus. This species is highly valued for its fruit, which is consistently large, juicy, and dark purple to black, possessing a balanced tartness and sweetness. M. nigra is a smaller, slower-growing tree, usually reaching about 30 feet, but it is exceptionally long-lived, with some trees surviving for hundreds of years. Unlike the other two, the fruit has a very short stem, making it slightly harder to pick.
Primary Uses of the Tree and Fruit
The mulberry tree has historically been significant, primarily serving as the foundation for sericulture, or silk production. The leaves of the White Mulberry (Morus alba) are the sole food source for the domesticated silkworm, Bombyx mori. The cultivation of this tree was intrinsically linked to the spread of silk manufacturing from ancient China into Europe and Asia.
The fruit is a versatile culinary ingredient, enjoyed fresh and used in preserved goods. Its sweet flavor makes it suitable for jams, jellies, pies, and wines. The berries contain anthocyanins and flavonoids, which contribute to the fruit’s vibrant color and antioxidant properties.
Growing and Maintaining a Mulberry Tree
Mulberry trees are hardy and adaptable, thriving best in full sun to partial shade and in moist, well-draining soil. While they tolerate a range of soil types, a loamy soil with a neutral to mildly acidic pH is ideal. When planting, consider the adult tree’s size and the messy nature of the fruit drop, which can severely stain concrete, paving, and driveways.
Pruning is an important management practice, but it must be done judiciously because mulberries are prone to “bleeding,” or profusely losing sap from cuts. The best time for pruning is during the tree’s dormant season in late winter or early spring before the buds turn green, as this reduces sap loss. Cuts should be limited to diameters no larger than two inches to ensure wounds heal effectively and avoid disease.