What is "rubus caesius"

Dewberry \Dew"ber`ry\, n. (Bot.)

1. The fruit of certain species of bramble ( Rubus); in England, the fruit of Rubus c[ae]sius, which has a glaucous bloom; in America, that of Rubus canadensis and Rubus hispidus, species of low blackberries.

2. The plant which bears the fruit.

   Feed him with apricots and dewberries.
   --Shak.

Rubus caesius is a Eurasian species of dewberry, known as the European dewberry. Like other dewberries, it is a species of flowering plant in the rose family, related to the blackberry. It is widely distributed across much of Europe and Asia from Ireland and Portugal as far east as Xinjiang Province in western China. It has also become sparingly naturalized in scattered locations in Argentina, Canada, and the United States.