I had to look up on the web about how to prune our Boysenberry and I discovered that once it has finished fruiting you cut off the old canes and tie up the new ones that are forming.
This was easier said than done! The old ones were all tied to chicken netting and extracting them without ripping my hands to shreds was tricky. Then the new ones were all entangled in my legs....Still, I have done my best and it doesn't look too bad.
I think next year it should be prolific as this year was its first "proper" year. Although we have had the plant since we lived in Christchurch, it has been moved several times and not really had a chance to establish itself.