How to Prune Blackberries

As winter continues to linger, some of you may be taking the opportunity to prune the orchard, including the small fruits, while the plants are dormant.

But before we tell you how to safely chop away at your blackberries, let’s address the different varieties of blackberries. Traditionally, most blackberries have borne fruit on two-year-old canes, called floricanes. Recently, however, some ever-bearing varieties have been developed; these bear fruit on one-year-old canes, or primocanes.

Primocane varieties have the potential to bear two crops—one in the summer from the second-year canes and one in the fall from the first-year canes. This is why they are considered ever-bearing. While this initially sounds like an advantage, fruiting on the first-year canes is typically only beneficial in northerly climates with late springs. Fruit from primocanes gets off to a later start start than fruit from floricanes, enabling it to ripen in the cool fall when moisture is abundant. After harvest, the canes are typically cut to the ground, as northern growers generally do not want to deal with the sparse summer harvest of the second-year canes.

However, primocane blackberries typically suffer in quantity and quality in climates where summer temperatures hit 90°F. Under these conditions, floricanes have the advantage due to their greater heat tolerance. This is probably why K-State blackberry variety recommendation lists typically only include the tried-and-true floricane varieties.

Therefore, we will only address the pruning needs of standard floricane blackberries in this post.

You Will Need

Pruning shears.
Lopping shears (good for tougher wood and reaching into brambles without getting scratched).
Gloves (thick ones if you are dealing with thorny varieties!).

Instructions

Winter Pruning

Cut down all dead, diseased, or weak canes. Make sure your cut is as close to ground level as possible.
Thin out the remaining live, healthy canes to leave about four to six inches of space between every cane.
Trim lateral branches back to a length of 12 to 18 inches. Err on the shorter side if you frequently have problems with breakage. Not only does this part of the pruning process result in sturdier branches, but it will encourage the plant to put more energy into growing big, luscious berries rather than longer branches.

Post-Harvest Pruning

Cut down all canes that bore fruit during the summer. They will not bear again, and removing them immediately after harvest can reduce the risk of disease. You should have no difficulty identifying the canes that bore fruit, as they will likely have evidence of old flowers and fruits remaining on them. They will also have very hard, woody stems. Make sure your cut is as close to ground level as possible.
Cut down all canes that have escaped the beds.
Trim new canes (thick, fleshy, greenish canes that did not bear fruit during the growing season) back to a height of four feet. If the first-year canes are less than four feet tall, just nip off an inch or two of the tip. This encourages the growth of lateral branches, which is where the next season’s fruit will grow. It will also cause the cane to thicken up and become stronger and less top-heavy.
If you are using a trellis, this is a good opportunity to train the canes.

A Few Final Tips

If your blackberry plants are healthy, feel free to compost the pruned material. Just be sure to chop up anything hard or unwieldy to encourage faster composting. But if your blackberries are suffering from any disease issues, you will probably want to burn the pruned-out canes to avoid the spread of disease.

Regularly cleaning your pruning shears is advisable when dealing with diseased plants. Use a solution of 1 part bleach to 10 parts water.