The genus Morus, commonly known as mulberries, comprises several species of deciduous trees and shrubs that have spread across the globe. Determining their native origin is complicated because extensive human cultivation over millennia has obscured the wild boundaries of most species. The three most recognized types—identified by their fruit or bark color—each trace their ancestry back to a different, geographically separate region. Widespread planting for fruit production and silkworm farming has led to a global distribution that often masks their true homes.
The North American Native: Red Mulberry (Morus rubra)
The Red Mulberry, Morus rubra, is the sole mulberry species native to the North American continent. Its historical range extends across the eastern and central United States, from southern Ontario and Massachusetts south to Florida, and west to Texas and Nebraska. This species thrives primarily in moist, rich soils, often found in river valleys, floodplains, and along stream banks.
Morus rubra typically grows as an understory tree in mesic hardwood forests, demonstrating a preference for sheltered coves and low-lying areas. It is a medium-sized tree, often reaching heights of 35 to 50 feet with a rounded canopy. The leaves are usually larger than other mulberries, featuring a rough, sandpaper-like texture on the upper surface and a soft, densely hairy underside.
Indigenous peoples utilized the fruit, consuming the sweet, dark purple to nearly black berries fresh or incorporating them into preserves. Today, the species is considered threatened or endangered in parts of its northern range due to habitat loss and hybridization. The native Red Mulberry is vulnerable to genetic pollution from the introduction and aggressive spread of its non-native relative, the White Mulberry.
The Asian Origin and Global Dispersal: White Mulberry (Morus alba)
The White Mulberry, Morus alba, originated in the mountainous regions of northern China, and possibly parts of India. Its history is inextricably linked to the global spread of sericulture, the practice of raising silkworms for silk production. The leaves of Morus alba are the preferred and almost exclusive food source for the domesticated silkworm, Bombyx mori.
The tree’s importance to the silk trade spurred its intentional cultivation and dispersal along ancient trade routes, including the Silk Road, leading to its establishment across Asia, the Middle East, and eventually Europe. Its introduction to North America began in the colonial era in the 1600s, when attempts were made to establish a domestic silk industry. For example, the Virginia legislature once mandated that every male resident plant a certain number of White Mulberry trees.
These early attempts at sericulture in the Americas largely failed due to climate and economic factors, but the introduced trees quickly escaped cultivation. Morus alba is incredibly adaptable, tolerating a wide range of climates and poor soil conditions, allowing it to naturalize aggressively across the continent. Its rapid growth, prolific seed production, and ability to hybridize with the native Red Mulberry have established it as an invasive species globally. Unlike the Red Mulberry, its leaves are typically shinier and smoother, though the fruit color can vary widely from white to pink or dark purple.
The Western Asian and European Cultivar: Black Mulberry (Morus nigra)
The Black Mulberry, Morus nigra, is highly valued for its large, intensely flavored, dark purple fruit, which many consider superior for culinary use. Its precise native range is challenging to define, but is generally accepted to be the region of Western Asia, likely encompassing modern-day Iran, Afghanistan, and the surrounding areas of the Armenian highlands. The fruit, known in Persian as shah-toot or “king’s mulberry,” suggests its ancient and esteemed status in its homeland.
The dispersal of Morus nigra throughout the Mediterranean and Europe occurred long before the arrival of its Asian cousin, Morus alba. Its spread was primarily driven by the desire for its fruit, not for silkworm cultivation, which distinguishes its history from the White Mulberry. It was cultivated in ancient Greece and Rome, with evidence of its presence in the Southern Levant dating back to antiquity.
Due to this long history of cultivation, which spans many centuries and pre-dates accurate botanical records, the Black Mulberry’s true wild populations are difficult to distinguish from naturalized plantings. While it has an established presence across Europe and the Mediterranean today, it is not native to these regions. The Black Mulberry found in European orchards is a result of ancient human selection and transport from its original Western Asian home.