Blackberry GRowing in central SD
We don't have much data on the performance of the Darrow blackberries in South Dakota. I have one in my backyard in Rapid City which died back to the crown when exposed to minus 24 or so the first winter, but the recommendation is to cut all the canes back the first winter anyway. This year the canes all appear healthy - we've barely gotten down to minus 18 or so. They will need a lot of space, and fruit on 2nd year canes. Tipping (removing 3-4 inches) of the current-season branches in early summer (when they reach 3 to 4 ft tall) will help form extra fruiting buds. Cut out all canes that have fruited after fruiting - they will die then anyway.