Pruning is essential for a good blackberry crop. Traditional single-crop blackberries bear fruit on two-year old canes called floricanes. They grow new primocanes each summer which will produce fruit the following year. Everbearing blackberry varieties have new floricanes and primocanes growing and producing throughout the year.
Different pruning methods for traditional and everbearing blackberries are recommended. Pruning either type of blackberry consists of removing the spent floricanes and leaving the new primocanes to set new fruit.
Use curved-blade pruning clippers that are good and sharp. Make quick, clean cuts. Prune out dead canes by cutting them an inch or two above the crown of the plant, being careful not to damage nearby canes. The crown of the plant is at soil level, where the canes emerge. Wear gloves if you are working with thorned varieties.
Blackberries will always have two kinds of canes, fruiting canes, and non-fruiting canes. Primocanes are the non-fruiting canes. Prune primocanes to a desired height (3 to 4 feet) to promote sturdier upright growth and to encourage lateral growth. Blossoms and fruit will be on the lateral growth.
The canes that bloom and bear fruit are the floricanes. These were previously primocanes, and after pruning and growth will now bear fruit. Floricanes should be pruned out after fruiting to allow the plant's energy to go towards developing healthy primocanes for the next round of fruit production.
Traditional, single-crop blackberries produce fruit biennially. This year's primocanes will be next year's floricanes. Each spring, the plants grow new primocanes that develop over the summer. Tip-prune the new primocanes during the growing season to control their height and length and to encourage lateral growth.
Only the two year old floricanes will produce fruit. Allow them to blossom and fruit. Once the berries are harvested, prune out the floricanes at the plant's crown. This allows the plant to focus on growing strong primocanes for the next year's berries.
Floricanes on single-crop blackberries are rather woody, while primocanes generally have softer, greener growth.
Everbearing blackberries follow the same general primocane to floricane growing pattern, except it is not on a biennial timetable. Some of the spring primocanes will produce berries early that year. They should be pruned out after fruiting to allow the second round of canes to produce fruit later in the season, usually in early fall.
Tip-prune the non-bearing primocanes to encourage heavier lateral growth and fruit set. More primocanes will grow throughout the summer.
Everbearing blackberries should have all floricanes pruned out in the fall after fruit production ends. Remaining primocanes can be tip-pruned in the fall, or in the late winter before they come out of dormancy.
To make clean cuts, use curved-blade pruning clippers that are sharp.
In late winter, prune out apparent winter damage. In early spring, remove dead canes that do not come out of dormancy.
Destroy old canes to prevent plant diseases. Do not use trimmings or leaves for mulch.