For my third article in our series on pruning fruit bushes I’m tackling raspberries and blackberries (for other fruit bushes see the links to Part 1 and Part 2 at the end of this article). It’s just great to find plants such as these that can be classed together. Immediately you know what to do with two plants instead of one, even though they might at first appear completely different.
Raspberries and blackberries couldn’t really have more different habits, one growing canes tall, upright, stately, the other sending out arching, lounging, extremely long arms that will embrace the whole garden if you’re not careful. Both, however, bear their fruit on canes grown the previous year, and that’s pretty much all you need to remember when pruning. (Yes, some of you are shouting "Autumn raspberries!" at the screen at this very moment, but they’re dealt with below. Here I’m talking about summer-fruiting raspberries.)
Pruning Summer-Fruiting Raspberries
Cut down fruited canes as close to the ground as possible. Ideally you should do this as soon as they’ve fruited. They will die off anyway, but removing them sooner rather than later has a couple of advantages. One, they won’t be a drain on the plant’s energy, which will then be concentrated into the new canes, destined to bear next year’s fruit; two, they won’t shade the new canes from sunlight, so the latter will develop better. The taller and stronger the new canes are at the end of the summer, the more fruit you’re likely to pick next year.
If you’re worried about which canes to cut down, then look for the empty hulls of last year’s fruit. They’ll be on the branching canes. New canes are smooth and unbranched.
Still, it’s not the end of the world if you don’t prune them out then and, as is the way of things, I tend to find myself cutting them down in late winter, when doing other pruning.
Raspberries are one of those plants that throw up suckers, so you need to keep an eye open for those and cut them off at ground level. Weedy ones should be got rid of completely but, if you want another raspberry plant, dig out a robust-looking sucker and plant it where you’d prefer it to be.
Despite their different habit, blackberries are treated the same way as summer-fruiting raspberries. Fruited canes are cut right back, the current year’s new growth left to fruit next year.
I have to admit to allowing my rather rampant blackberry to grow in a hummock. This isn’t recommended in the best gardening circles, and surely makes tidy gardeners blanch, as new canes tend to reach out and root themselves where they touch the ground (which is great if you want more bushes – just dig up and replant). It also entails some careful manoeuvring when it comes to reaching into the bush to remove fruited canes at the base.
However, I’ve never got round to putting in any posts and wires. For those who are much tidier than I am, one of the most efficient approaches is to set up posts and wires to the left and the right of the blackberry plant. The idea (called the "alternate bay system") is that you train all the canes grown in one year onto the wires on one side of the plant, (say, to the left), and all the canes the following year on to the wires on the opposite side. This means that all those to the left fruit at the same time and are cut down together, to be replaced with the new canes growing in the year when all those to the right are fruiting.
Again, if you’re at all worried about deciding which are the fruited canes, then just look for clusters of empty hulls that remain on the branches.
Pruning Autumn-Fruiting Raspberries
These are generally grown to fruit on canes grown in the current year. (I say, generally, as some people do aim to get two crops, one in early summer from last year’s late growth, but we’re going for the simpler approach.) Just cut all the canes down to ground level in winter, and that includes any new canes that might have poked their heads up towards the end of the previous year.
You can, if you like, and especially if you fear a late bout of severe weather, wait until the new growth starts in spring, as the old canes will give some protection to the crown. However, don’t delay cutting down the old canes once the new growth starts, and don’t muddle up last year’s growth with the new season’s.
If the new canes come up thick and fast in spring, then it’s a good idea to decongest the plant by taking out the weaker looking shoots, but I find that most of the time you can leave them to get on with things.
For Part 1 of this series on How to Winter Prune Gooseberries and Currants, Click Here. For Part 2 of this series on How to Prune Blueberry Bushes, Click Here.