Thornless cultivars produce sweeter fruit than the original evergreen blackberry. 'Chester' and 'Hull' are two thornless cultivars with good fruit production and a sweet flavor. Boysenberry is not extremely acidic, but offers a sweet-tart flavor.
Loganberries are juicy, but very acidic. Tayberry blackberries also produce acidic fruit, though not as much so as the loganberry.
Less acidic-tasting blackberries taste best fresh, while others work well frozen or made in to preserves. Thornless cultivars produce the sweetest berries, with boysenberries and Cherokee blackberries also offering an excellent fresh taste.