How to Prune Prime Jim Jan Blackberries

Monitor the growth of your blackberry plant after planting. The first year shoots, primocanes, need little attention and may not produce fruit. Periodically pinch off the top of the primocane while wearing gardening gloves once it grows 3 feet. This step forces the canes to form branches, and the gardening gloves protect your hands from thorns.

Use pruning shears to "mow" the primocanes so that 16 inches of blackberry cane remains above ground. Do this in the winter when the plant is dormant, clearing away snow if necessary.

Install lattice or wire fencing behind the blackberry canes. In the spring, secure the growing canes to the fencing using twine or plastic ties. The fencing helps support to the vine when it is heavy with fruit.

Prune the tips of the floricanes in June, before the blackberry cane forms flowers. Floricanes are second-year canes that produce fruit before dying. Cut the top of the cane down 6 to 12 inches to force the plant to form lateral branches. These branches flower and produce fruit. More branches mean larger berry yields.

Remove dead floricanes by cutting the cane at ground level using the pruning shears. This helps produce strong, sturdy vines during the next season. Use lighter fluid and matches to burn the remaining vine to prevent disease. The blackberry plant will grow new canes in the spring.