Blackberry plants can be a bit challenging if pruning is not done on a regular basis. There are two basic types of blackberries: erect and semi-trailing. They can be thornless or thorny, so care must be taken to wear the appropriate protective clothing when working with the thorny plants. Thornless blackberries grow slower and are easier to handle, thus more popular with the home gardener than the thorny type. Blackberries are trained to trellises, much like grapes, for their ease of care and harvesting. Most gardeners grow blackberries for use in jams, cooking desserts and eating out of hand.
Trimming Semi-trailing Blackberries
Allow trailing canes to grow on the ground for the first year. Place them in the direction of the row. Trim the tops back in late winter 1 inch if the canes seem strong and you had a good crop of fruit during the season, and 4 or 5 inches if the canes are weak and you did not have a good crop.
Tie the new 4- to 6-foot shoots to a trellis in the second and third growing season with soft cotton string. Tie them out on the wire in a fan shape so the branches can get air circulation between them.
Remove older brown shoots after harvest. Cut off any damaged, dead or diseased shoots along with them and burn or discard them in a waste receptacle. These shoots should be cut as close to the ground as possible.
Cut lateral shoots back to 12 to 14 inches in late winter or early spring before the new growth starts.
Trimming Erect Blackberry Plants
Cut the tips from erect blackberry plants when they reach 30 to 36 inches. This will encourage lower, thicker branching that will hold a heavier crop.
Tie the canes to a one-wire trellis when they reach 4 feet in height with soft cotton string. In June or July, trim the new green shoots on the trellis back to just above the trellis.
Cut off damaged, dead or diseased shoots whenever you notice them. Burn or discard the debris in a trash receptacle to avoid causing disease to the healthy plants.
Trim the brown older shoots or floricanes back to the crown of the plant after harvest. Discard of these shoots in the same manner as the dead ones.
Trim lateral shoots to 12 to 14 inches in the late winter or early spring before new growth starts.