Garden Variety: Winter upkeep key for health of berries
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Pruning raspberry and blackberry plants improves fruit yield and quality, makes fruit more accessible for harvest, maintains size of plantings and reduces pest problems. Late winter is an ideal and important time to prune these plants in Kansas.
Raspberry and blackberry plants are referred to collectively as brambles or caneberries. Pruning recommendations for this group of plants are often overly complicated because of differences in growth habits and horticulturist lingo. However, there are some general things that can be done to improve the overall health of any bramble patch and late winter is the best time to perform the work.
First, go through the bramble patch and remove all dead, dying, damaged, and diseased canes (stems). Cut the canes at ground level with pruners or loppers. This removal helps reduce insect and disease pressure and opens up the patch for harvest of fruit in the coming growing season.
Once the dead and unhealthy canes have been removed, thin the remaining canes by selecting the healthiest stems and removing the rest to ground level. Try to reduce the number of canes to three to six canes per square foot unless you know the variety and have a more specific recommendation.
Remember that brambles are suckering plants, so new shoots will appear between the canes that are left once new growth begins in spring. Thinning allows more light to reach plants, increasing fruit production and easing harvest. Many gardeners err on the side of being overly cautious with thinning – finding the right balance can be a learning process from year to year.
To go beyond dead/unhealthy cane removal and thinning, knowing the growth habit of the brambles in question is necessary. There are primocane and floricane varieties of raspberries and blackberries, and erect/semi-erect varieties of blackberries, all with their own requirements.
Primocanes refer to the new, first-year growth produced by bramble plants. Floricanes are the second-year growth. Brambles are biennial, so floricanes die at the end of the season. There should be a constant cycle of primocanes and floricanes in a bramble patch unless being managed differently.
Some raspberry and blackberry varieties produce fruit on primocanes and are known as primocane, fall-bearing and/or ever-bearing varieties. Other varieties produce fruit only on floricanes and are known as traditional, summer-bearing or summer-fruiting varieties. The tricky part is that primocane varieties may produce over the summer and start producing around the same time as floricane varieties.
For primocane-fruiting raspberries and blackberries, there are two methods of pruning. The first option is to cut the entire patch to ground level in late winter. New shoots that grow in the spring will produce a crop once they get large enough to flower and fruit.
The second option for primocane-fruiting raspberries and blackberries is to selectively prune out dead canes and thin the remainder as described above. The benefit of this is that the second-year canes (floricanes) produce fruit in the summer earlier than the primocanes which means a longer season of harvest. The downside is that this method is considerably more labor-intensive.
Examples of primocane-fruiting raspberries are Anne, Autumn Britten, Fallgold, Heritage, Himbo Top, Jaclyn, and Joan J. Examples of primocane-fruiting blackberries are Prime-Jim, Prime-Jan, and the Prime-Ark series.
Summer-fruiting (floricane) red raspberries are next. These only produce fruit on second-year canes. Remove dead/unhealthy canes as described above and thin plants to three to four per square foot. Latham is a classic summer-fruiting red raspberry variety.
Summer-fruiting black raspberries, purple raspberries and erect blackberries have similar growth habits. For these, remove dead/unhealthy canes as described above and thin the remaining live canes to three to six per square foot. Examples of this group are Jewel (black raspberry); Brandywine and Glencoe (purple raspberries); and Arapaho, Apache, and Ouachita (erect blackberries).
For this group of brambles, a little additional pruning is recommended. First, trim back lateral branches to 12 to 15 inches long at the same time that plants are thinned. Then, during the summer, cut tips off the primocanes as needed. For black raspberries, tip canes when they grow to about 30 inches tall. For purple raspberries and erect blackberries, tip canes when they reach 36 to 40 inches tall. Tipping encourages production of lateral branches.
The next group is semi-erect blackberries. They are pruned similarly to erect blackberries by removing floricanes, thinning remaining stems and trimming lateral branches in late winter each year. The main difference is that these plants are usually grown on a trellis or other support system. Tie stems to the supports as they grow and wait until canes are five feet long to tip them during the growing season. Examples of semi-erect blackberry varieties are Triple Crown, Chester and Hull.
— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation.