The question of whether to cut back blackberry bushes in the fall is one of the most frequent sources of confusion for gardeners. Blackberries are popular and productive garden fruits, but their pruning needs change depending on the specific variety being grown. Understanding the growth cycle of your particular bush is the single most important factor for maximizing fruit yield and maintaining the long-term health of the plant. Proper pruning involves timing cuts precisely to the plant’s natural life cycle, rather than simply cutting everything back at the end of the season.
Floricanes and Primocanes: Knowing Your Bush
The key to correctly pruning blackberries lies in distinguishing between the two types of canes the plant produces. While the crown and roots are perennial, the individual canes are biennial, meaning they live for two years. This two-year cycle determines where and when the fruit develops.
First-year shoots are called primocanes; their growth is purely vegetative, focusing on height and strength. Once a primocane successfully overwinters, it becomes a floricane in its second year.
Floricanes transition to reproductive growth, producing flowers and fruit during the summer season. After the floricane has produced its harvest, it dies back completely and will not fruit again. An established blackberry plant will have both new primocanes and fruiting floricanes growing simultaneously.
Pruning Standard Floricane Varieties
Standard, summer-bearing blackberries, including most erect and trailing varieties, are floricane-fruiting types. For these traditional varieties, the primary pruning event in the fall is the removal of the spent canes, done immediately after the harvest ends in late summer or early fall.
The floricanes that produced fruit this season should be cut back completely to the ground level. Removing these dead canes increases air circulation and reduces the risk of disease spread. This action directs the plant’s energy toward strengthening the new primocanes that will bear fruit next summer.
Major pruning for shaping and managing the remaining new primocanes is reserved for late winter or very early spring during the dormant season. At this time, thin the canes, leaving only the strongest four to six primocanes per plant. The lateral branches on these remaining canes should also be headed back to a length of 12 to 18 inches to encourage bud development.
Pruning Everbearing Primocane Varieties
Everbearing blackberries, such as varieties like ‘Prime-Ark,’ fruit on the tips of the first-year primocanes in late summer or fall. This unique growth habit allows for a significant fall pruning cut, offering two distinct methods for managing the harvest.
The simplest approach is the single-crop method, which involves cutting all canes down to the ground level after the fall harvest is complete and the plant is dormant. This is typically done in late fall or early winter. This method sacrifices the potential summer crop but results in a single, large, high-quality harvest the following fall. This technique is often preferred in colder regions where canes may not successfully overwinter for a summer crop.
Alternatively, the double-crop method allows for a smaller summer harvest followed by a fall crop. In this system, only the portion of the primocane that fruited in the fall (usually the top third) is removed. The remaining lower section is left to overwinter, becoming a floricane that produces a second, earlier crop the following summer. After this second crop, the cane is completely removed at the base, similar to traditional floricane varieties.
Sanitation and Winterizing After Pruning
Regardless of the blackberry type, proper sanitation immediately following pruning is necessary to prevent the carryover of pests and diseases. All removed canes, laterals, and plant debris should be gathered and destroyed, either by burning or discarding, rather than composting. Diseases like cane blight or rust can easily overwinter on infected material, posing a threat to the healthy remaining canes.
Once the area is cleared, the plants benefit from a layer of organic mulch, such as straw or wood chips, applied around the base. This layer helps regulate soil temperature, conserves moisture, and protects the crown from extreme cold during the dormant winter period. For trailing or semi-erect varieties, ensuring the remaining canes are securely trellised or tied provides support and minimizes damage from heavy snow or high winds.