On young, vigorous shoots, the leaves may be up to 30 cm (12 in) long, and deeply and intricately lobed, with the lobes rounded. On older trees, the leaves are generally 5–15 cm (2.0–5.9 in) long, unlobed, cordate at the base and rounded to acuminate at the tip, and serrated on the margins. Generally, the trees are deciduous in temperate regions, but trees grown in tropical regions may be evergreen.

The flowers are single-sex catkins; male catkins are 2–3.5 cm (0.8–1.4 in) long, and female catkins 1–2 cm (0.4–0.8 in) long. Male and female flowers are usually found on separate trees although they may occur on the same tree. The fruit is 1–1.5 cm (0.4–0.6 in) long. 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 380 miles per hour (610 km/h), about half the speed of sound, making it the fastest known movement in the plant kingdom.