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You prune thornless blackberries in spring by cutting back the previous year’s canes while leaving the new green growth untouched.
Spring pruning is one of the most important jobs for keeping your thornless blackberries productive and easy to manage.
If you’ve been wondering how to prune thornless blackberries in spring without messing up next summer’s harvest, you’re in the right place.
In this post, we’ll walk through the exact timing, the simple steps, and the common mistakes to avoid when you prune thornless blackberries in spring.
Let’s dig in.
Why You Should Prune Thornless Blackberries In Spring
Pruning thornless blackberries in spring is all about directing the plant’s energy toward new fruiting canes.
Thornless blackberries are biennial, meaning each cane lives for two years.
The first year, the cane grows vegetatively and is called a primocane.
The second year, that same cane flowers and produces berries, and it’s then called a floricane.
After fruiting, that floricane dies back naturally.
So when you prune thornless blackberries in spring, you’re removing those dead or weak floricanes to make room for fresh primocanes that will fruit next year.
1. Spring Pruning Boosts Berry Size
When you prune thornless blackberries in spring, you reduce the number of canes competing for water and nutrients.
This means the remaining canes get more resources, and the berries that develop will be noticeably larger and sweeter.
Crowded blackberry thickets produce small, seedy fruit, but a well-pruned plant rewards you with plump, juicy berries.
2. Spring Pruning Prevents Disease
Thornless blackberries are prone to fungal diseases like anthracnose and cane blight, especially when air can’t circulate through the plant.
When you prune thornless blackberries in spring, you open up the center of the plant, allowing sunlight and breeze to reach every cane.
This dry, airy environment keeps spores from taking hold and spreading.
3. Spring Pruning Keeps Harvesting Easy
Nobody wants to fight through a thorny mess, but even thornless varieties can become a tangled jungle if left unpruned.
When you prune thornless blackberries in spring, you keep the plant neat and upright, so you can reach every berry without scratching your arms or bending over awkwardly.
When To Prune Thornless Blackberries In Spring
The best time to prune thornless blackberries in spring is just after the last hard frost but before new growth really takes off.
In most climates, that lands between late February and early April.
You’ll know the timing is right when you see tiny green buds swelling along the canes but before the leaves actually unfurl.
Pruning too early in late winter can expose the canes to frost damage.
Pruning too late in mid-spring wastes the plant’s energy, because it’s already pushed out new growth that you’ll have to cut away.
Signs It’s Time To Prune Thornless Blackberries In Spring
Look for these signs that it’s time to prune thornless blackberries in spring:
– The soil is no longer frozen and can be worked easily.
– Buds are starting to swell but haven’t opened into leaves yet.
– You can clearly see which canes are brown and brittle (dead) versus green and flexible (alive).
If you miss that early window, you can still prune thornless blackberries in late spring, but you’ll sacrifice some of the current season’s fruit.
How To Prune Thornless Blackberries In Spring Step By Step
Now let’s get into the actual process of how to prune thornless blackberries in spring.
It’s a simple job that takes about 15 minutes per plant.
Grab a pair of sharp bypass pruners, thick gardening gloves (even for thornless types, the bases can be rough), and a pair of loppers for thicker canes.
Step 1: Remove Dead And Damaged Canes First
Start by identifying every cane that is brown, brittle, or snapped.
These are the old floricanes that fruited last summer, and they won’t produce again.
Cut them all the way down to the ground, not just at the top.
Stubs left behind can rot and invite pests.
When you prune thornless blackberries in spring, this first pass removes about one-third of the plant’s total mass.
Step 2: Thin Out Weak And Thin Primocanes
Next, look at the green, living canes that grew last year.
These are your primocanes, and they’ll fruit this summer.
But you don’t want all of them.
Keep only the thickest, healthiest canes, about 4 to 6 per plant for a typical backyard bush.
Cut the skinny, spindly ones at the base.
Crowded canes compete for light and produce poor fruit.
Step 3: Shorten The Remaining Canes
Once you’ve thinned to your best 4 to 6 canes, shorten each one.
Cut the top off so the cane is about 4 to 5 feet tall.
Make the cut just above a healthy outward-facing bud.
This tip pruning encourages lateral branches to form along the cane.
Those laterals are where the berries will actually grow.
Step 4: Tie The Canes To A Trellis
After you prune thornless blackberries in spring, the remaining canes need support.
Use soft plant ties or twine to secure each cane loosely to a wire trellis or a fence.
Don’t tie too tightly, as the cane will thicken as it grows.
Space the canes about 6 to 8 inches apart along the wire.
This keeps the plant open and airy for maximum sun exposure.
Common Mistakes When You Prune Thornless Blackberries In Spring
Even experienced gardeners can make a few slips when they prune thornless blackberries in spring.
Here are the three most common errors and how to avoid them.
1. Cutting All The Canes Down To The Ground
Some folks mistakenly treat thornless blackberries like perennial flowers and cut everything back to the soil.
Big mistake.
If you cut the green primocanes down to the ground, you’ll have zero fruit this summer, because those are the canes that produce berries.
Always remember: dead canes go to the ground, but living canes just get shortened.
2. Pruning Too Late In The Season
If you wait until the leaves are fully open to prune thornless blackberries in spring, you’ll be cutting off active growth and reducing yield.
The plant has already spent energy pushing out that growth, so you’ve wasted its resources.
Aim for that swollen-bud window, and you’ll be fine.
3. Leaving The Cuttings On The Ground
Don’t leave the pruned canes lying around the base of the plant.
They can harbor fungal spores and overwintering pests.
Bag them up and toss them in the trash, not the compost pile, unless your compost gets hot enough to kill pathogens.
So, How To Prune Thornless Blackberries In Spring?
You prune thornless blackberries in spring by removing dead floricanes, thinning weak primocanes, and shortening the remaining canes to about 4 to 5 feet.
Do this in late winter or early spring when buds are swelling but leaves haven’t opened yet.
Keep 4 to 6 healthy canes per plant, tie them loosely to a trellis, and clean up all your cuttings.
Follow these steps on how to prune thornless blackberries in spring, and you’ll enjoy a bigger, sweeter, and easier harvest all summer long.
Now grab your pruners and give your blackberries the spring haircut they deserve.