Late winter or early spring, just at the end of the dormant season, is the best time to prune summer-bearing red raspberries. Here's how.
If you didn't remove the old canes right after they fruited last summer, take those out first. Then thin the canes that will bear this season's crop. Prune out all the smaller ones, leaving fruiting canes four to six inches apart in a bed that's about a foot wide.
Next, you can shorten the canes that are left, but easy does it! According to Marvin Pritts, a small fruits specialist at Cornell University in Ithaca, New York, the most fruitful portion is the top third of the cane. If you are in the habit of cutting your canes back by half (leaving them about three feet tall) so they will be self-supporting, you are sacrificing half your potential crop.
The top portion of the cane is most fruitful because the buds are spaced more closely there. So the only portion you should remove is the very tip, where the cane becomes thinner or somewhat undersized. Buds that formed there late last season are not strong and often suffer winter damage.
Most varieties should be five or six feet tall after you've finished pruning. For support, fasten the canes to a trellis, which can be as simple as a single strand of wire set slightly lower than the tops of your canes. Later in spring, remove the first flush of new replacement canes when they get six inches tall. Such early cane removal increases the crop by 20 to 50 percent.Jack Ruttle is a former editor at National Gardening.