My black raspberries are in their third year. I have just pruned out the spent floricanes, which fruited very abundantly. However, the primocanes are 5-6 feet tall, with most of their growth in the top foot, because I didn't know to prune them when they were about 3 feet tall, i.e. in June. The canes are relatively sturdy; they just don't have many laterals below 3.5 feet. When I have done pruning before, I've cut just beyond a leaf, thinking that would promote branching. However, the leaves down below are threesomes, spaced about 6-8 inches apart along the lengths of the canes. It's older growth down there, not the growing tip; so I don't know how well that part of the plants would respond to pruning.

Is it too late to be pruning back the primocanes? I don't mean their laterals, but the actual canes themselves. And, if it's not too far along in the season, how far down should I prune? I'm afraid that if I don't do some pruning, I'm just going to have fruiting next year in that top foot of the canes. Conversely, I don't know whether such drastic pruning as cutting the top 1.5--2 feet off the canes at this point in the season wouldn't just kill 'em.

What do you advise?