How to prune blackberries

The work is worth it for the baskets of berries you will harvest

Blackberries have an interesting life cycle. Individual plant crowns and root systems live for many years. The shoots, called canes, that grow from these crowns each live for only two years. New canes arise from the crown every year. During their first year, these new canes, called primocanes, focus their energy on growing length and foliage. In their second season, the canes bear fruit and die. Second year canes are called floricanes.

Blackberries are pruned three times a year, in winter, summer and fall. The specific tasks differ for each of these pruning events, but the overall goal is the same: encourage healthier plants and larger, higher quality fruits. This may seem like a lot of work, but the pruning involved is quick and simple once you know what to cut.

Winter Pruning

In late winter, from February through early March, floricanes that will produce this year’s fruit are thinned and trimmed. Thinning is simply reducing the number of canes that will be left to produce fruit. In addition to encouraging larger fruits, thinning also makes harvesting easier and increases air circulation, which discourages diseases.

We want to leave four or five strong canes per plant. If you are growing blackberries in a row, leave three to five canes per linear foot. Start by removing damaged or diseased canes, cutting them at ground level. Then remove short, spindly canes. Leave four to five of the strongest floricanes. New canes will develop from the crown during the growing season while floricanes are flowering and setting fruit. These new primocanes will produce next year’s fruit.

Next, trim the lateral or side branches on the remaining canes. These side branches grew last season and may be quite long. Trimming them causes the plant to focus energy on ripening fewer fruits, which increases berry size and quality. Shorten later branches to a length of 12 to 15 inches, making cuts just above a bud.

Summer Pruning

First season primocanes are pruned during the summer months. As new canes grow, they can become long and a bit unruly. To encourage better fruit production and make our plants more manageable, prune primocanes between mid-June and mid-July by cutting canes to a height of three to four feet. This type of pruning is called tipping and causes lateral branching near the top of the cut cane. These side shoots are where next summer’s fruit will be produced. Not all canes will reach the proper height for tipping at the same time. Continue to tip canes as smaller stems reach chest height. If you are using a trellis, tie canes to the trellis wire as you prune them.

Fall Pruning

By fall, the season’s floricanes have completed fruiting and are ready to be removed. Cut off the old stems near the crown of the plant or ground level. If you are having trouble distinguishing a floricane from a primocane, look for a woodiness to the bark and old flower clusters still clinging to the tips of branches.

Remove clippings from the garden every time you prune. Dead canes can harbor disease and insect pests; they need to be disposed of or burned rather than composted on site.