I have these old horribly overgrown blueberry bushes on old farmland my family owns. These plants haven't been touched in maybe 12 years and some are 10+ feet tall/thick. My question is if i prune them now are they too old to produce? I'm assuming i will have to cut them all all the way back to produce anything in the coming years. Wondering if anyone has any experience with these things any help is very much appreciated. THANKS!!