I decided to prune this cane more aggressively and was able to take pictures inside. I was wrong, the cane with the strange leaves does have 3 normal laterals, in addition to the closely spaced minis. The normal looking cane actually branches off of the strange one, at a low point on the rose, and the small leaves begin about 8 inches above that, which I didn’t notice before I cut it. I’m wondering if it was over sprayed and the the small leaves are the new growth from this year, but I don’t have pictures to compare.

To me your branches look fine and not like weedkiller afflicted canes. Good luck!

Thank you! They look strange to me, but this is the longest I’ve had a climber last in this spot because I didn’t choose hardy enough varieties. I moved my other climbers to the front of my house where they’re doing better, but they are more delicate, flexible types and they don’t have nearly this many leaves, so maybe this confirms it’s a better choice for this location. A few weeks ago I cut back a lot of the canes from the matching Abe Darby on the other side of the garage door (it’s a year older and grafted though) and it’s started pushing out tons of these same tiny leaves, so maybe it’s just thriving more than I’m used to.