How To Prune Thornless Blackberries

Learning how to prune thornless blackberries is the single most important skill for a healthy, productive patch. These vigorous plants absolutely require annual cutting back to focus their energy on big, sweet berries instead of a tangled mess of canes. With the right technique, which is simpler than you might think, you’ll enjoy much larger harvests for years to come.

All blackberries, including thornless varieties, grow on a two-year cycle. In the first year, new green shoots, called primocanes, emerge. They grow leaves but do not flower. These canes overwinter and become the second-year floricanes. In their second spring, these now-brown, woody canes produce lateral branches that flower and fruit. After fruiting, those floricanes die. Pruning manages both types of canes at the right time.

This main process involves two major pruning sessions per year: a summer “tipping” and a winter cleanup. Sticking to this schedule keeps your plants under control and maximizes fruit production.

Essential Tools for the Job

You don’t need fancy equipment, but sharp, clean tools make the work easier and protect plant health.

Bypass Pruners (Hand Shears): For most cuts on canes up to ½ inch thick.
Loppers: For thicker, older canes at the base; their long handles provide leverage.
Sturdy Gloves: Even thornless types can have minor prickles or rough stems.
Disinfectant: Rubbing alcohol or a bleach solution to clean blades between plants, preventing disease spread.

The Summer Prune: Tipping for More Fruit

This is done in late spring or early summer, when new primocanes are about 3 to 4 feet tall. The goal is to encourage branching.

Identify the healthy, new green primocanes growing from the crown.
Using your pruners, cut off the top 3 to 6 inches of the cane’s tip.
This signals the cane to stop growing upward and instead send out lateral branches from buds lower down.

These laterals, or side shoots, are where next year’s fruit will form. More laterals means more berries. Without tipping, you often get just one long, unruly cane with few fruiting branches.

The Winter Prune: The Big Cleanup

This is your main pruning effort, done in late winter when the plant is fully dormant. The leaves have fallen, making the structure clear. A good rule of thumb is to do this about a month before your last expected spring frost.

Remove All Dead Canes: First, cut out all the floricanes that fruited last summer. They will be brown, woody, and brittle. Cut them off as low to the ground as possible and remove them from the patch.
Thin the Primocanes: Now look at the primocanes you tipped last summer (they will have turned brown or reddish-brown over winter). Choose the 4 to 6 healthiest, strongest canes per plant or per linear foot of row. Remove the thinner, weaker ones at the base.
Shorten the Laterals: On the canes you kept, look at the lateral branches you created from summer tipping. Prune these side shoots back to about 12 to 18 inches in length. This concentrates the plant’s energy into the remaining buds, resulting in larger berries.
Tie or Weave: Finally, attach the remaining canes to your trellis or support system. This keeps them organized, improves air circulation, and makes picking easy.

What About Everbearing (Primocane-Fruiting) Thornless Blackberries?

Varieties like ‘Prime-Ark Freedom’ can fruit on first-year canes in the fall. You have two options:

For Two Harvests: In winter, remove only the top portion of the cane that fruited in fall. The lower buds will fruit the following summer. Then, after that summer harvest, remove the entire cane.
For One Big Fall Harvest: The simpler method is to cut all canes down to the ground in late winter. The plant will send up new canes that will fruit in the fall. This sacrifices the early summer crop but often leads to a more robust fall harvest and easier management.

Training Systems for Support

A good support system makes pruning and harvesting a breeze. Two common methods are:

Treillis System: Use T-shaped posts with wires running along the arms. Train the floricanes to one side and the new primocanes to the other. This keeps them seperate and is very organized.
Fan System: Attach canes to a fence or wall in a fan shape. This is great for small spaces and looks attractive, allowing good sunlight penetration.

Common Pruning Mistakes to Avoid

Even experienced gardeners can slip up. Here’s what to watch for:

Pruning at the Wrong Time: Major removal of canes in spring or fall can severely reduce your crop or encourage disease.
Not Pruning Enough: Being timid leads to overcrowding. Plants need light and air to stay healthy and produce quality fruit.
Making Ragged Cuts: Dull tools crush stems. Always use sharp bypass pruners for a clean cut that heals fast.
Leaving Debris: Always remove and destroy (don’t compost) the cut canes. They can harbor pests and fungal spores over winter.

Aftercare Following Pruning

Your plants will appreciate a little care after their haircut.

Apply a balanced, slow-release fertilizer in early spring as growth begins.
Mulch around the base with wood chips or straw to conserve moisture and suppress weeds.
Ensure they recieve about 1-2 inches of water per week, especially when fruit is developing.

FAQ: Thornless Blackberry Pruning

When is the absolutle best time to prune thornless blackberries?

The major cleanup prune is best in late winter, during dormancy. Summer tipping is done when new canes reach 3-4 feet tall.

Can I prune my blackberries in the fall?

It’s not recommended. Fall pruning can stimulate new, tender growth that will be killed by frost, and open wounds may not heal before winter, inviting disease.

How short should I cut the lateral branches?

During the winter prune, cut back the lateral branches on your floricanes to 12-18 inches. This is a key step for bigger berries.

What do I do if my blackberry bush is completely overgrown?

Don’t panic. In late winter, cut every single cane down to the ground. It seems drastic, but it will reset the plant. It will send up new shoots, though you may sacrifice one season’s fruit. Then, follow the annual pruning schedule from then on.

Why didn’t my thornless blackberries produce fruit?

The most common reason is pruning error—accidentally removing all the second-year floricanes. Other causes include too much shade, improper watering, or a lack of essential pollinators in the area.

Mastering how to prune thornless blackberries is a rewarding garden skill. It might feel counterintuitive to cut back so much growth, but this practice is what ensures your plants remain vigorous, healthy, and loaded with fruit. With consistent annual pruning, you’ll enjoy an abundant harvest from your thornless blackberry plants for many seasons to come. Remember the simple cycle: tip in summer, clean up in winter, and always remove the old canes that have finished their job.