Pruning holds a mystique for me. It’s the purview of the elite, experienced horticulturist, not a bush-leaguer like me; a craft bordering on art in its extreme forms, and it scares me.
My first experience with pruning, other than hacking away at overgrown hedges, was with roses. I read all about forming a bowl shape, maintaining air circulation, where to cut to encourage new growth in a certain direction.
That was twenty years ago and still my rose-pruning method is to address the plant, flash back upon the tutorials I’ve pored over in the past two decades, and then start hacking off whatever has been grabbing my clothes as I pass by.
Blackberries are different. They’re yummy. So I’m more serious about them than roses. Here, I’ll explain some of the basics about blackberries and show how to prune them to encourage production and keep them under control.
My blackberries are upright thorny blackberries. The instructions here apply also to upright thorn-less blackberries. Their growth is similar, though not as aggressive as the thorny variety.
To prune blackberries, first you have to know blackberries.
Blackberries fruit on second-year growth. That’s known as a biennial fruiting habit. Lovely fancy terminology. More of that to come. Don’t be intimidated by the words. It just means that, like many flowers, such as Sweet William, you plant it one year, it puts out green leafy growth only. The next year, it will flower, and in the case of the blackberry, it will make blackberries. You can tell first year growth (called primocanes–prim0=first, see?) from second year growth (called floricanes–flori=flower, easy!) by their appearance. Primocanes look fresh, green, and new, with lots of tender growth at the tips, (and no flowers or fruit) throughout the growing season. Like this:
In this next photo, compare the primocane on the right to the floricane on the left. The floricane, in addition to the obvious flowers, has darker, more mature leaves here at the tip compared to the primocane.
Now you know your floricanes from your primocanes, let’s talk about pruning.
The most basic, pruning 101 is removing floricanes after fruiting is over. They will not bear fruit again, and removing them is crucial to keeping your blackberry bushes from looking like a celebrity mugshot hairdo. Those old canes will hamper new growth, encourage disease, and make harvesting next year’s crop more difficult. Here’s a spent floricane:
Follow it down to the ground, cut it off at the crown (where it emerges from the ground), pull it out (wear heavy gloves if yours have thorns) and discard it. Keep going until you’ve pruned them all out. Done. Easy.
The second type of blackberry pruning is known as tipping. This is done throughout the growing season. Blackberry canes want to send out long runners, several feet long, at the expense of branching growth. This makes your bushes look more like giant spiders than shrubs. This characteristic is called apical dominance. The tip (or terminal bud) of those long canes contains a hormone called auxin which actually inhibits the growth of the lateral (or side) branches. Naughty terminal bud. What we want is lots of lateral growth and thicker canes for more places for blooms and berries and stronger canes to support those big, juicy berries.
So what we do is cut off those naughty terminal buds so the canes will be able to branch out, get stout, and produce more fruit. In this photo I’m showing you some of the lateral shoots that will grow and beef up the cane once the tip is removed from the end of the cane they are on:
See the little leaves trying to grow? In the next photo, check out the lateral growth that has begun on this cane which was pruned a few days ago. This is what we want.
Keep your canes trimmed back to from 24 to 48 inches long, depending on how compact you want your blackberry bushes to be. And once those lateral branches that you’ve encouraged to grow get over 18 inches long, tip them back, too.
So now you know how to have tidy, productive blackberries, clear out some space in the pantry for some of this jam.