Wild black raspberries in containers. What canes to prune when, please. Link’s good.
These were volunteers, I let them grow into more boxes. Some years fruitful, bounty, others not. Think it's my nonpruning, or wrong pruning.
Certified GKH Gardening Expert
If they have not had root pruning, then this will be the cause. They can tolerate being rootbound, but only to a certain extent. After this point they will begin to degrade.
You will have to pull the plants out, and prune out the largest roots to the base of the root ball, and replant.
Pruning the tops isn't completely necessary, but they can benefit from a pruning right after the fruit is mature and pulled off. Leave plenty of old cane sticking out of the ground so that you can get a good fruit set the next year.
This article will help you more with care of black raspberries: https://www.gardeningknowhow.com/edible/fruits/raspberry/pruning-black-raspberry-bushes.htm