Boysenberry Plant – Live Plant The Boysenberry Plant is a cross between raspberry, blackberry, Dewberry and Loganberry and was created in 1923 by Rudolph Boysen. Walter Knott of Knott’s Berry Farm acquired the Boysenberry Plant and was the first to commercially cultivate the berry in Southern California and named it after it’s creator, Rudolph Boysen. Boysenberries are eaten fresh or made into juice or preserves. Boysenberries look much like an elongated blackberry and, like blackberries, have a dark purple color and a sweet flavor with a hint of tartness. The Boysenberry plant is a vining perennial that grows in USDA zones 5-9, and like full sun. Plants are shipped in 2-1/2? pots.