Dormant Pruning Your Blackberries & Raspberries
Raspberries really benefit from winter pruning. Once the second year canes fruit they will die and can be cut back right after fruiting or in the dormant season. Remove damaged, weak or dead canes by pruning at ground level. Leave canes that are robust (about 1/4” in diameter), but thin out canes to about 6” apart. You should keep your raspberries to about a 2’ wide hedgerow. Since raspberries spread by underground runners, the berry patch can get quite large if not thinned out. Dig up any plants that have escaped the 2’ wide row. You can either plant these in another area of your yard, share them with friends or put them in your compost bin.
Blackberries have three possible growth habits—erect, semi-erect or trailing. The way to train and prune them will depend on the type. If you did not top the new canes during the late summer, you should top them to about 5’ (or the height of your trellis or fence). Dormant pruning of erect blackberries entails removing dead canes (color is brown vs a newer green cane) and cutting back laterals to 12–18”. Semi-erect blackberries should be thinned to 5 to 8 of the strongest canes, shorten the laterals to 12–18” and remove any growing on the lower 3’ section of the main canes. Tie to a fence or trellis to provide support. Trailing blackberries are less cold tolerant and in cold regions the canes can be left on the ground and protected with rowcover or mulch over the winter. In spring the canes can be lifted and tied to a trellis at 3’ and 6’.