As we look into the corner of the Gardenerd Test Garden, we see the need for blackberry pruning. Someone else in the Gardenerd community did the same thing and asked: “I believe you mentioned it is time to prune blackberries, but what’s your method? My Seattle friends say they all cut the plants off at ground level and tear out the runners invading new territory. My plants are 2 years old. What is best pruning method for the maximum yield next year?”
Before we prune blackberries, let’s talk about how they grow:
For the sake of simplicity, let’s say blackberries have floricanes: they fruit on second-year canes. This means that a cane (or stalk) will grow tall in the first year, but it will only set fruit in the second year and then it will die back. So if you want fruit every year, cut down only the canes that fruited this spring/summer.
Some people tie ribbons around the canes that fruited, but we just wait until those fruited canes die back and turn brown, usually in winter. Step One: Cut all the brown canes back to soil level and leave the green canes for next year. Leave 5-6 green canes for each plant.
Step Two: Tip-prune green canes back to 4 feet above ground. This will help generate bushy new growth when the time comes. You can also prune any lateral branches (side shoots from the main canes) back to 12″ inches.
Step Three: Dig out those runners! Blackberries are vigorous runners. Those runners can travel across the yard. Our blackberry plant started as a cutting in a pot, it now pops up as far away as ten feet from the original plant.
Dig runners out with a shovel and follow them back to the source as much as possible. Runners send up new canes all along its length so be vigilant. A little effort every couple of months will restrict blackberries only to designated areas.
Note – there are different types of blackberries and other cane berries. Some have canes that don’t die back at the end of the season, and some have both primocanes (that fruit in the first year) and floricanes. These instructions work for blackberries with floricanes but may not apply to raspberries or black raspberries that have a primocane-growth behavior. If your plant doesn’t exhibit the growth behavior mentioned above, read up on the variety you’re growing to be sure you are pruning the way it wants to be pruned.