Mulberry is the primary food plant for the caterpillars that produce commercial silk.
Silkworms are the larvae of the domesticated silk moth, Bombyx mori. They feed mainly on leaves of white mulberry, Morus alba, although other mulberry species can also be used. The caterpillar converts nutrients from the leaves into silk proteins and spins a cocoon before becoming a moth.
White mulberry originated in Asia and was spread widely through the history of sericulture. Its leaves are especially suitable because they are nutritious, abundant, and available during much of the silkworm-rearing season.
A common misunderstanding is that mulberries themselves produce silk. The tree supplies the food; the insect produces the silk filament. Silk production also uses other moth species in some regions, but Bombyx mori and mulberry cultivation are the classic pairing of sericulture.