The mulberry tree takes its name from its fruit, which looks like an elongated blackberry or raspberry. There are three species of mulberry, which vary in size and habitat. Their berry color may be deep purple, red, pink or white, depending on the species. Some newer fruitless cultivars have been produced to serve as ornamental trees.
The red, or American mulberry (Morus rubra), is a native of the eastern half of the United States. The white mulberry (Morus alba) is native to eastern and central China, but became naturalized in North America when it was introduced by the early colonists for silkworm production; it is regarded as a weed tree in many parts of the country. The black mulberry (Morus nigra) is originally from western Asia; hardy only to zone 7, in the U.S. it is limited mainly to the Pacific coast.
All mulberry species are deciduous, but they vary as to when they leaf out. The leaves of the white mulberry appear in early spring, weeks before those of the black mulberry. The mulberry’s oval leaves are a bright, glossy green and irregularly lobed, turning yellow in the fall. White mulberries can reach 80 feet, and can also be pyramidical or weeping in form. Red mulberry trees may reach up to 70 feet. The black mulberry is much shorter, reaching only 30 feet, and unless trained tends to grow as a multi-stemmed shrub. The three species differ greatly in longevity, since it is unusual for a red mulberry tree to survive more than 75 years, while a black mulberry may produce fruit for hundreds of years.
Although people think of the mulberry as being a berry, it is technically an aggregate fruit, consisting of smaller fruits called drupes. The color of the fruit changes as it matures, going from red to a deep purplish-red. Unlike the blackberry and raspberry, a stem stays on the fruit after it is picked. Although the fruit can be messy if it falls on sidewalks and driveways, it is very attractive to wildlife, and can be used to make pies, jams and preserves.
Mulberries and Silkworms
Silkworms, which eat nothing but the leaves of the white mulberry, have been cultivated in China for thousands of years, where their silk is used to create beautiful fabrics. Some plant scientists, most notably Luther Burbank, have sought to engineer better mulberry trees to increase silk production, says Dr. Thomas Ombrello of the Union County College Biology Department.
Mulberries are attractive and undemanding trees, given adequate room. The California Rare Fruit Growers, Inc. website recommends a space of at least 15 feet between each tree. Keep mulberries away from sidewalks to avoid staining. They require a location in full sun and prefer a well-drained deep loam. They need little fertilization, and are resistant to drought, requiring water only during dry seasons.