Blackberries are perennial plants with root systems that last from year to year, but their stems, known as “canes,” are biennial, lasting only two years before being replaced by new growth. Proper pruning is essential to maintain the health and productivity of your blackberry plants. Here’s a detailed guide on how to prune blackberries effectively.
Part 1: Initial Pruning
Step 1: Prune Part of the Stem
When planting a blackberry vine as a rooted cutting, prune off two-thirds to three-fourths of the handle or stem, leaving only a short crown behind. This stimulates the buds at the crown of the cutting, encouraging them to grow more vigorously.
- Crown of the Cutting: This refers to the portion of the cutting that extends just above ground once planted.
- Removing Damaged Tissue: Cutting off most of the stem also removes any potentially damaged or diseased tissue.
- Timing: Do this pruning after you have already planted the cutting in the ground.
- Established Plants: If you are planting a seedling, bush, or vine with well-established erect canes, do not prune them back.
Step 2: Cut Back the Canes During the First Winter
First-year growth is usually poor, so late during the first winter, cut back the canes until they are roughly 3 to 4 inches (7.6 to 10 cm) high. This encourages the plant to develop sturdier canes that can support more fruit.
- Satisfactory Growth: If you are satisfied with your first-year growth, pruning back the canes so dramatically may not be necessary. Follow standard annual pruning requirements instead.
Part 2: Annual Summer Pruning
Step 1: Remove Floricanes After the Harvest
As soon as you harvest the berries from one floricane, remove the entire cane from the plant by cutting it off at its base, near the main stem. Floricanes are usually second-year canes and are responsible for producing the majority of the plant’s fruit. They are spent after producing fruit, which is why you should remove them.
- Identifying Floricanes: Only remove the canes that bore fruit that year. You should be able to see visible fruit stalks on the canes even after the berries have been removed.
Step 2: Head the Primocanes
Once each primocane has exceeded its desired height by roughly 4 inches (10 cm), head it back down to its desired height. Primocanes are new or “first-year” canes. They usually start as green shoots but should mature by fall, changing into woody brown canes.
- Heading Heights:
- Vigorous, erect blackberries: 48 to 60 inches (122 to 152 cm) above ground.
- Less vigorous erect blackberries: 36 to 48 inches (91 to 122 cm).
- Semi-erect blackberries: 4 to 6 inches (10 to 15 cm) above the top trellis wire.
- Benefits of Heading: Heading causes the cane to stiffen, allowing it to support the weight of fruit and foliage better. It also encourages lateral buds in the primocanes to develop into lateral branches, which are the plant’s fruiting branches.
Step 3: Make Space
Periodically clean out canes if the plant gets too crowded. This increases the amount of light received by the plant and the airflow between plants, helping the blackberries grow better and reducing the risk of disease.
- Row Width: Maintain a row width of 18 to 24 inches (45 to 60 cm) at the base of the rows by cutting back low base canes once they threaten to crowd each other out.
- Removing Weak Primocanes: Remove weak primocanes when you cut off dying floricanes after your floricane harvest. During active growth, primocanes are considered weak when they exhibit poor foliage growth, appear damaged, or show signs of disease.
Step 4: Trim Root Suckers
Allow root suckers to develop into rows up to 12 inches (30 cm) wide. Once they grow beyond this point, trim them back down to a width of 12 inches (30 cm) or less. Root suckers grow out of the crown or base of the plant and do not develop fruit, stealing crucial energy from the rest of the plant.
Part 3: Annual Winter/Spring Pruning
Step 1: Wait Until Late Winter
Heavy dormant pruning should be performed once the plants are well into dormancy and just before they return to a state of active growth. Late winter and early spring are best. Harsh winters can injure the tips of canes and laterals, so wait until most of the winter passes to address these damaged spots during pruning.
- Disease Prevention: Performing the majority of your heavy pruning during the dormant season decreases the occurrence of wounds that can invite diseases like cane blight.
Step 2: Prune Back All the Primocanes
Shorten all of the primocanes on your plant by about one-third their current height. This encourages lateral fruiting shoots on the lower portion of these canes to branch out in the spring, focusing the plant’s energy on fruit-producing branches.
Step 3: Thin Out the Lower Primocanes
For upright blackberries, thin out the new primocanes produced from root buds and crown buds so that there are only six or eight canes per linear foot (30 cm) of row. If your blackberry plant does not produce root buds and only produces crown buds, remove weak canes measuring less than 1/2 inch (1.25 cm) in diameter at the base, then thin out the remaining new primocanes until there are only five or six per hill.
Step 4: Cut Back Lateral Branches
Most lateral branches should be trimmed back to a length of 12 to 18 inches (30 to 45 cm). This encourages larger fruit to form since you are forcing the plant to spend its energy in a more concentrated space.
- Vigorous Canes: Leave the lateral canes a bit longer on vigorous canes and a bit shorter on slower canes.
- Winter Damage: If you notice winter damage on a lateral cane, cut it back far enough to remove this damage, even if it shortens the branch more than usual.
- Air Circulation: Completely remove lateral branches from the lowest 18 inches (45 cm) on vigorous canes and from the lowest 12 inches (30 cm) on weaker canes to improve air circulation, minimizing the risk of disease and making harvest easier.
Step 5: Remove Damaged and Dead Canes
Any weak or damaged canes that have not already been removed by this point should be pruned. Weak canes include any cane with a diameter less than 1/2 inch (1.25 cm) at its base. Canes that rub or intertwine with one another should also be removed, as well as damaged, diseased, or dead canes to prevent the possible spread of disease or insects.
By following these steps, you can ensure that your blackberry plants remain healthy, productive, and beautiful. 🍇