Hi, I'm having problems with my black raspberry bushes this year. I have 6...

Asked July 7, 2013, 11:08 AM EDT

Hi, I'm having problems with my black raspberry bushes this year. I have 6 plants on the south side of my house. With all of the rain we've been having this year, the new primacanes are growing like crazy. So much so, that they're starting to break under their own weight. I topped them mid-May. Normally, I like to wait longer, but they'd already gotten so long I felt I needed to. They're topped to about 4ft each cane. We were out of the country for the whole month of June, and when we came back, the laterals had just grown like crazy. See attached picture. I've cleared out the spent floricanes and tried to tie up the central primacanes to keep them from breaking under the weight of the laterals, but the bushes are now over 6 ft high, still growing like mad, and it's only the beginning on July! I'm worried that the plants are just going to break/choke under their own weight if they keep going. So my questions are: *What can I do to better support the plants? Do I need a trellis system? Seems a little late, as the laterals are fairly well established growing every which way. It would have to be fairly tall, too. *If a trellis is called for, what type? T posts, V posts, something else? Is there a good adjustable solution you know of? *Can I cut the primacanes back to a more reasonable height this late in the game? If so, what would that be? Cutting them would take out a lot of established laterals, but if they'll grow back, I guess that wouldn't be a problem. Thank You! Dave Hill

Howard County Maryland

1 Response

We recommend that you prune black raspberry canes to 36-40" when the new canes come up in spring. Lateral should be pruned back to 12". (Easy to remember: yardstick for canes, ruler for laterals.)

Also prune out any weak canes thinner than a pencil.

With the weather we're having, the raspberries will keep growing all summer and will need one or probably more tip prunings. You are probably safe lowering the height a few inches, (though of course we can't guarantee that the current lush weather conditions will continue.) If the alternative is for the canes to break because they are too top heavy, you really have no choice, by all means prune them lower.

You shouldn't need a trellis system. Remove the old canes after fruiting and don't overfertilize. We recommend 1 lb. nitrogen per 10 foot row in spring each year.