How do I prune blackberries that fruit twice?

Question

So I purchased a few "Prime Ark Freedom" blackberries. They are a primocane fruiting variety BUT they fruit twice (once early on then once in the fall if temps/weather is right)

Right now I have about 4-5 plants in a corner (they are going a bit crazy but are still fruiting) but are VERY tall. Most of them seem to have 3 canes that go very high up and then droop over. I honestly have never pruned plants much in general but these seem like they need it.

I've heard it's a good idea to "top" them at maybe 4 feet? Does it matter where I cut?

Also when do I prune the cane back down to the ground? During winter I guess? Is there any point in letting the cane stay around another year.

Some of the canes look sorta dead but halfway up the cane (starting from the top back) I guess I should just cut these off to the ground I assume?)

Thanks! (Also do I need to worry about staking or tying these off? if they were trimmed down to 4 foot or so they would stand up on their own)

edit: Apologies, apparently these plants ALSO fruit on the floricanes too.

Answer 1

You can't do any "permanent" damage to blackberries by incorrect pruning, since the individual canes only live for two years and the plant is continually regenerating itself from the roots. The worst you can do is not get any fruit for a year!

You should have cut just the tip off the canes when they reached about 3 to 4 feet tall. That will encourage more canes to branch from lower down and produce a bigger crop, and avoid ending up with a ridiculously tall plant. If blackberries are left to "run wild" along the ground, the canes may get to 10 feet long or more, but that won't work if you are growing them vertically.

In late winter, cut off all the dead and damaged canes at ground level. If plant looks "too big" for its location, cut back more of the old canes to ground level, but if you want two crops next year, don't cut back all of them. If you cut the entire plant down to ground level, you will only get one (late) crop next year.

If you now have some over-long canes where the top half is dead, cut them back just into the living part. As the first sentence said, if that causes any issues they will sort themselves out when those canes die completely next year.

Blackberries are naturally very strong and fast growing plants - "4 to 5 in a corner" may be "3 to 4 too many" for the space available. It that is the case, don't try to move the old plants. Just bend a cane down to ground level and hold the top 2 or 3 feet along the ground (using rocks, bricks, or anything available) and it will root and start a new plant. You can then cut the old cane and move the new plant while it is still small and easy to handle.