Morus alba, known as white mulberry, is a fast-growing, small to medium-sized mulberry tree which grows to tall. It is generally a short-lived tree with a lifespan comparable to that of humans, although there are some specimens known to be over 250 years old. The species is native to northern China and India, and is widely cultivated and naturalized elsewhere. The white mulberry is widely cultivated to feed the silkworms employed in the commercial production of silk. It is also notable for the rapid release of its pollen, which is launched at over half the speed of sound. Its berries are edible when ripe.
Description
On young, vigorous shoots, the leaves may be up to long, and deeply and intricately lobed, with the lobes rounded. On older trees, the leaves are generally long, unlobed, cordate at the base and rounded to acuminate at the tip, and serrated on the margins. The trees are generally deciduous in temperate regions, but trees grown in tropical regions can be evergreen. The flowers are single-sex catkins; male catkins are long, and female catkins long. Male and female flowers are usually on separate trees although they may occur on the same tree. The fruit is long; in the species in the wild it is deep purple, but in many cultivated plants it varies from white to pink; it is sweet but bland, unlike the more intense flavor of the red mulberry and black mulberry. The seeds are widely dispersed in the droppings of birds that eat the fruit. The white mulberry is scientifically notable for the rapid plant movement involved in pollen release from its catkins. The stamens act as catapults, releasing stored elastic energy in just 25 µs. The resulting movement is approximately, about half the speed of sound, making it the fastest known movement in the plant kingdom.
Taxonomy
Two varieties of Morus alba are recognized:
Morus alba var. alba
Morus alba var. multicaulis
Cultivation
Cultivation of white mulberry for silkworms began over four thousandyears ago in China. In 2002, 6,260 km2 of land were devoted to the species in China. The species is now extensively planted and widely naturalized throughout the warm temperate world. It has been grown widely from the Indian subcontinent west through Afghanistan and Iran to southern Europe for over a thousand years for leaves to feed silkworms. More recently, it has become widely naturalized in disturbed areas such as roadsides and the edges of tree lots, along with urban areas in much of North America, where it hybridizes readily with the locally native red mulberry . There is now serious concern for the long-term genetic viability of the red mulberry because of extensive hybridization in some areas.
Uses
White mulberry leaves are the preferred feedstock for silkworms, and are also cut for food for livestock in areas where dry seasons restrict the availability of ground vegetation. The leaves are prepared as tea in Korea. The fruit are also eaten, often dried or made into wine. For landscaping, a fruitless mulberry was developed from a clone for use in the production of silk in the U.S. The industry never materialized, but the mulberry variety is now used as an ornamental tree where shade is desired without the fruit. A weeping cultivar of white mulberry, Morus alba 'Pendula', is a popular ornamental plant. The species has become a popular lawn tree across the desert cities of the southwestern United States, prized for its shade and also for its cylindrical berry clusters composed of sweet, purplish-white fruits. The plant's pollen has become problematical in some cities where it has been blamed for an increase in hay fever.
