Pruning thornless blackberries correctly is a cycle of renewal that directly impacts the quantity and quality of the fruit harvest. The biennial fruiting habit of the canes means that a season’s work is an investment in the next year’s yield. Understanding the plant’s growth pattern and applying targeted pruning maximizes fruit production and maintains a healthy, manageable structure. This management directs the plant’s energy toward developing large berries rather than unproductive growth.
Understanding Cane Function
The high productivity of thornless blackberries depends on the distinct function of their two types of canes. While the plant is perennial, individual canes have a two-year life cycle. First-year shoots are primocanes, which are typically green and flexible, focused on vegetative growth without producing fruit. These primocanes emerge from the crown and develop the buds for the following year. After surviving winter, the primocane transitions into a floricane in its second year. Floricanes are woodier, darker, and produce the summer berry crop. Once a floricane finishes fruiting, it dies back completely and must be removed.
Seasonal Pruning for New Growth
The first active pruning occurs during the summer growing season and focuses on managing newly emerging primocanes. This technique is known as “tipping” or “heading back,” and it directly increases future fruit yield. When a primocane reaches four to five feet in height, its tip should be removed with a clean cut.
Removing the growing tip eliminates apical dominance, which concentrates growth at the tip. The cut forces the plant to divert energy into developing lateral branches from the buds below the cut point. More lateral branches create a greater surface area for flower and fruit development the following year, boosting the potential harvest size. This tipping process must be repeated as new primocanes continuously emerge throughout the summer.
Dormant Pruning and Cane Removal
The most important pruning occurs during late winter or very early spring while the plant is fully dormant. The primary goal is the complete removal of all spent floricanes that finished fruiting the previous summer. These older, dead canes are typically dry, brittle, and darker, and should be cut down to the ground level.
Removing dead canes is necessary because they will not produce fruit again and compete with new primocanes for light and air, potentially harboring disease or pests. After the dead wood is cleared, the remaining primocanes must be thinned to a manageable number, leaving only the strongest four to six canes per plant. Thinning concentrates the plant’s energy into the most vigorous shoots, leading to larger berries and improved air circulation. The final step is to shorten the lateral branches that grew after summer tipping, cutting them back to 12 to 18 inches.