Refereeing raspberries vs. blackberries
I planted a row of (coho) raspberries three years ago in our garden, and extended it last year with two thornless (ursinus) blackberry bushes, one of which over the summer has grown a vine twice as fat as the fattest ever of the raspberries and long enough to run across the four bushes of their row. Both of the blackberries seem to be continuing full speed, while the raspberries are taking it easy. Should I just allow to ensue what I guess could be a fight to the death? If so, should I stop cutting down the raspberry suckers that pop up in the blackberries's turf so they can fight with all their resources? And what else could or should I do with my fat ~20-30' blackberry vine besides letting it grow out of its support structure and across the four tripods that support the raspberries? There's nowhere I can let it go in the three other horizontal directions, and arranging for it to grow and ala Jack's beanstalk into the sky doesn't seem possible or likely to be rewarding. I'd be grateful for any advice or suggestions!
Multnomah County Oregon
Blackberries are very vigorous growers. Controlling even desirable ones can be difficult. The problem is that the primocanes, which will produce next year's crop can be very long - and impinge on your raspberry's territory. These primocanes can be trained on the trellis in late August, looping the canes several times around the trellis wires. That should get them out of the way of the raspberries. Pruning or tipping the primocanes during the growing season is not recommended. Floricanes (that produced this year's crop) can be removed, but they recommend leaving them up as long as possible, so the nutrients they produce can be moved back into the crown and roots. Growing Blackberries in Your Home Garden gives good information on growing blackberries.
For the raspberries, the floricanes (which produced this year's crop) can be removed now, in late summer. The primocanes (which will produce next year's crop) should not be pruned or tipped during the growing season (now) so the nutrients can flow back to the roots. Pruning should wait until January-March. Growing Raspberries in Your Home Garden gives good information on growing raspberries, including advice on fertilizing schedules, watering, pruning, etc.
Sorry to be slow when you were so prompt. Thanks! That was helpful. You might be interested to know that, though I chose your more positive advice, an ostensibly berry-wise person at Portland Nursery told me I should give up and replant the blackberries elsewhere. I suppose he may have assumed I didn't have the infrastructure to really tie up the blackberry. It's iffy, with the tripods, but I'm hopeful. I've got a kind of beehive hairdo of blackberry vines now.
Glad I could help - Thanks!