When (time of year) and how (secondary canes?) does one prune Blackberry...
Pruning blackberries depends on what type of blackberries you have. Most people nowadays have thornless varieties, but there are also erect and semi-erect varieties, as well as the new primocane-producting varieties.
Probably, this link will answer your question, but if not then send us another email with the type of blackberries you are growing:
Most pruning is done in the spring.