Answer: Thornless blackberries are more sensitive to cold than their thorny cousins and are generally safe to about 0 degrees F. Thornless blackberries are vigorous, erect or semi-erect plants and should be spaced 4-6 feet apart in a row to allow sunlight to penetrate the entire plant. Most cultivars are hardy in zones 5 or 6. You can certainly try growing one of the most hardy cultivars in your garden to see how it fares. 'Chester' fruits late in the season but provides very large, very sweet berries. It's hardy to -10F.
Q&A Library Searching Tips