The Best Time of Year to Trim Blackberry Vines

How Blackberries Grow

• Understanding how this berry grows helps you ensure the right type of pruning occurs at the right time. Blackberry plants are perennial; they will continue to grow and produce fruit for years, but the fruit-producing canes that sprout from the crown are biennial, lasting just two years. Primocane are the first-year canes where the new fruit buds develop and then go dormant in the winter, and the floricane are the second year of cane growth, producing the fruit before dying off.

Summer Pruning

• Cut the tips of primocanes early in the season once they reach 36 inches high. Trimming promotes heavy bud development along the cane and additional side-cane growth, which in turn will provide a high fruit yield the following year. Fast-growing primocanes may require a second snipping during the growth season. Prune floricanes to the ground when the fruit production is finished, removing any weak or damaged primocanes at the same time.

Late Winter or Spring Pruning

• Prune any canes that suffered winter damage, leaving up to eight healthy canes per plant. Prune back any side or lateral canes to 12 inches, ensuring the removal of any winter damage. Prune away weak, slow-growing canes less than 1/2 inch in diameter. Prune primocane-bearing cultivars -- which produce fruit on the canes grown in the current season -- to the ground in late winter or early spring. Primocane-bearing plants require no further pruning throughout the season.

Ongoing Pruning

• Prune the stems of new plantings to force fresh canes to start growing. Pruning new plants also removes any disease that may be lingering along the stem. As needed throughout the year, remove any damaged or diseased canes to reduce potential pest problems, increase air circulation throughout the plant and eliminate the spread of disease. Keeping the plants free of debris also allows for good light distribution, which helps to provide plump, healthy berries.