How to Prune blackberry?
Cutting out old canes, and shortening new ones, helps retain some measure of control but plants may need cutting to the ground every few years

blackberry · Rubus fruticosus
Also known as: bramble; bumble-kites; common blackberry; common bramble
Can be fan-trained to provide fruit, but more suited to a wildlife garden. Tolerates most soils and situations, but need sun to flower and fruit well. May have the potential to become a nuisance if not managed well. See also blackberry cultivation for more advice
Cutting out old canes, and shortening new ones, helps retain some measure of control but plants may need cutting to the ground every few years