Charles Rudolph Boysen ( July 14 , 1895 â `` November 25 , 1950 ) was a California horticulturist . Charles Rudolph Boysen ( July 14 , 1895 â `` November 25 , 1950 ) was the California horticulturist who created the boysenberry , a hybrid between several varieties of blackberries , raspberries , and loganberries .