Dead canes are not difficult to identify. They are a much lighter color than live canes and are dry and brittle. These canes should be removed and discarded. The remaining canes should be thinned but the type of growth determines exactly how this should be done.
Black and purple raspberries and thornless blackberries: These tend to grow in a clump. Remove all the canes but 5 to 7 of the largest and healthiest in each clump. Cut back the remaining canes to living tissue if there was winter damage. With black raspberries, eight to 10
buds per lateral (side shoots) are usually enough. Cut laterals back to leave the recommended number of buds. Purple raspberries and thornless blackberries are more vigorous than black, so leave a few more buds per lateral. Thornless blackberries will also produce a few suckers that come up some distance from the clump. These should be removed or dug and transplanted to increase the planting.
Red raspberries and thorny blackberries: These two sucker badly and will fill the row with new plants. Prune out small canes within the row so that there are strong canes 4 to 6 inches apart. Head back all the remaining canes to about 5 feet. There is no need to prune back any laterals present. Keep aisles free of new suckers during the summer by mowing.
Everbearing red raspberries and blackberries: We now have what is called ever-bearing red raspberries and everbearing thorny blackberries. These are the exception to the rule in that they will bear fruit on first-year canes. Therefore, you can cut all canes to the ground in the winter and still have fruit. Examples include Heritage red raspberry and Prime-Jim, Prime-Jan, Prime Ark 45 and Prime Ark Freedom blackberries. For more detail and line-drawings that illustrate pruning techniques, see our publication titled, “Raspberries and Blackberries” at http://www.ksre.ksu.edu/bookstore/pubs/mf720.pdf. (Ward Upham)