Blackberry plants require some pruning or training through the planting year, and erect and trailing blackberry bushes have slightly different pruning needs. Blackberries can become unmanageable if not pruned each year. Pruning regularly can help you maintain a tangle-free patch.
TIP: Our expert gardening advisor, Rachel Klein cautions you, "If your bushes are of a thorned variety, make sure to wear gardening gloves and long sleeves before attempting pruning of any kind."
Erect cultivars are usually more winter-hardy than trailing blackberry bushes. They don’t need to be protected in winter.
Step 1 - Remove New Primocanes In Summer
Primocanes are the actively growing vegetative canes. Essentially, the new growth. In one year, the primocanes will mature into floricanes, the old growth fruit producing canes. Once the fruit has been harvested, the floricanes will eventually die.
In erect blackberry plants, remove the top 1 to 2 inches of new primocanes when they reach 3 feet tall, usually in late June to July. This will cause the canes to branch, and they will produce fruit the following year.
TIP: Rachel adds, "Hand pruners are great for tipping canes."
After harvest, use loppers to remove the floricanes at the root crown. These 2-year old canes will die by the end of the current growing season. Removing the floricanes immediately after the fruiting season will discourage disease and infection.
TIP: Rachel advises, "Never prune floricanes before or during the fruiting season, since they bear all the berries, except if they are damaged or diseased."
Step 2 - Tip Lateral Canes
In the late winter, use hand shears to cut back lateral (horizontal) canes to 12 to 14 inches. This will help greatly in allowing better access for harvesting and will encourage larger berries.
Step 3 – Thin Primocanes In Late Winter
When the plants are dormant, thin the primocanes to 3 or 4 of the blackberry plants’ strongest canes. If you have multiple plants in a row (hedgerow), thin 1 large cane every 5 inches in the row. Prune all lateral branches on these canes to a length of 12 to 18 inches.
Erect blackberry plants grown in a hedgerow will benefit from a trellis consisting of 2 wires, one on each side of the row, and at a height of 3 to 5 feet. This prevents the canes from bending into the aisles.
Step 1 – Train New Primocanes In Spring
In most types of trailing blackberry bushes, new canes are produced at the crown of the plant in the spring. They grow upright for a while and then turn down and trail along the ground. To avoid injury to these new primocanes, it’s best to keep them trained in a narrow row.
TIP: Rachel suggests, "When the primocanes reach 3 to 4 feet tall, top them by cutting off the top 1 to 2 inches of growth. This will encourage lateral growth and in turn, a larger harvest."