Botanically, a mulberry is not a berry but a collective fruit, in appearance like a swollen loganberry. When the flowers are pollinated, they and their fleshy bases begin to swell. Ultimately they become completely altered in texture and color, becoming succulent, fat and full of juice. In appearance, each tiny swollen flower roughly resembles the individual drupe of a blackberry.
The color of the fruit does not identify the mulberry species. White mulberries, for example, can produce white, lavender or black fruit. White mulberry fruits are generally very sweet but often lacking in needed tartness. Red mulberry fruits are usually deep red, almost black, and in the best clones have a flavor that almost equals that of the black mulberry. Black mulberry fruits are large and juicy, with a good balance of sweetness and tartness that makes them the best flavored species of mulberry.
The refreshing tart taste is in some ways reminiscent of grapefruit. Mulberries ripen over an extended period of time unlike many other fruits which seem to come all at once.