Like so many allotment plots ours was full of couch grass when we took it over. Have been fairly vigilant in keeping new growth out but unfortunately there is now a large clump surrounding one of our blackberry canes. So far its not affected the blackberry but how could I get rid of it. Its too intertwined to dig out. I am reluctant to dig out the blackberry! Have assumed any use of weedkiller would affect the blackberry. Any suggestions?