The reason for keeping them apart has nothing to do with cross-pollination. One often sees advice to keep red raspberries away from black raspberries to keep the reds from transmitting diseases to the less hardy blacks.

Similarly one reads that it is advisable to keep all raspberries several hundred feet away from wild blackberries because the wild plants may carry diseases which could infect the raspberries. If one is growing disease-free tame blackberry plants that probably wouldn't be as much of an issue, but we have a lot of bramble diseases in my area so I try to keep mine apart just to be on the safe side.

Good luck with your brambles.

thanks for clearing that up! No wonder I couldn't find that information anymore! ha!

Yikes! Last year I planted thornless blackberries in a row right beside my now-3-year-old raspberries. I thought I'd be able to mow the path between them and pull any RBs coming up in the BB patch and vice versa. I didn't know about the disease issue in the earlier post (didn't do my homework, guilty as charged) but I also didn't think that the new RB shoots coming up in the BB patch would look so similar to the BB shoots -- I can't tell the difference so don't know what to weed out! Big duh.

Does anyone know of a way to distinguish the two young shoots, other than waiting until they're big enough to see if they're canes (RBs) or vines (BBs)?

Otherwise, are my only other options to (a) install a root barrier around both beds, like 9" of aluminum roofing, or (b) dig out the BBs and move them much further away? I suppose (c) is to wait it out and see who wins ;-)

I planted Blackberry bush 3 feet from my raspberries. THEY DID CROSS POLLENATE, and Raspberries are BLACK, and very TART!!!

I want to find out how far away to move the Blackberries!