The White Mulberry (Morus alba) is a short-lived, fast-growing, small to medium sized mulberry tree, which grows to 10–20 m tall.
On young, vigorous shoots, the leaves may be up to 30 cm long, and deeply and intricately lobed, with the lobes rounded. On older trees, the leaves are generally 5–15 cm long, unlobed, cordate at the base and rounded to acuminate at the tip, and serrated on the margins. The leaves are usually deciduous in winter, but trees grown in tropical regions can be evergreen. The flowers are single-sex catkins, with catkins of both sexes being present on each tree; male catkins are 2–3.5 cm long, and female catkins 1–2 cm long. The fruit is 1–2.5 cm 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 insipid, unlike the more intense flavour of the Red Mulberry and Black Mulberry. The seeds are widely dispersed by birds, which eat the fruit and excrete the seeds.
The White Mulberry is scientifically notable for the rapid plant movement of the pollen release from its catkins. The flowers fire pollen into the air by rapidly (25 µs) releasing stored elastic energy in the stamens. The resulting movement is in excess of half the speed of sound, making it the fastest known movement in the plant kingdom.
It is also used to treat fever, headache, red dry and sore eyes, as well as cough.
The "White Mulberry Tree" is title of a crucial chapter in Willa Cather's 1913 novel, O, Pioneers, in which the two forbidden lovers are killed. A reference to the story of Pyramus and Thisbe.