Ask a Master Gardener: Whip underperforming raspberries into shape
Q. We have a red raspberry plant that is about 8 years old and is fairly small. It will flower but produces little fruit. Fruit is very small. It seems to flower with stops and starts throughout June, July, August and September. It is not trellised and I’m not sure how to prune it due to not knowing if it is considered summer bearing or everbearing.
A. It sounds like you have an everbearer. You will have to do some detective work to figure this out. Observe to see if the raspberries are blooming on first year growth in the fall. It’s easy to tell first-year canes from second-year canes. First-year canes have green stems, while the bark of second-year canes has turned a darker red-brown.
Fall bearing (primocane) raspberries produce fruit at the top of first-year canes in late summer. First year canes are called primocanes. If allowed to overwinter, these same canes (called floricanes the second year) will produce flowers and fruit again in early summer of the second year. While this type is considered “everbearing,” the early summer second-year crop is inferior, as you describe and new growth makes harvest more difficult.
With this type, it is easiest to cut the old canes to the ground in winter or early spring every year, and skip the less productive spring crop. Cut canes as close to the ground as possible so that buds will break from below the soil surface. If canes are not cut low enough, fruiting laterals may form on any remaining cane portion. These fruiting laterals will not be healthy. Ideally cutting to the ground is done December through February. The more new canes per square foot, the more fruit in general for this type.
Summer-bearing (floricane) raspberries produce fruit only from buds on second-year canes. Second year canes are called floricanes. Unlike fall (primocane bearing) raspberries, the canes must remain in place throughout the winter and following growing season, before fruiting the second year. If you cut the canes to the ground on this type in spring, you will have no fruit this year. The canes will have to overwinter, and bear next year.
With summer bearing, the largest berry size and yields come from a combination of selective pruning of first and second year growth. Various pruning techniques are used for summer-bearing raspberries. Here, fruit size decreases as cane numbers increase.
One pruning method is to select the healthiest primocanes (new growth) in late spring to grow for fruiting in year two. Leave three to five canes per linear foot.
Cut the other less healthy or rejected primocanes to ground level when they are 8 inches tall. Ignore primocane regrowth until the dormant season (December through February). Then remove these short canes. Spring pruning of floricanes should be delayed until winter injury on overwintered canes can be identified, usually by mid-March or early April. Summer bearing red raspberries are best trellised so all the flower buds are left to produce fruit.
More information at:
Ÿurbanext.illinois.edu/raspberries
Ÿweb.extension.uiuc.edu/macon/palette/080706.html
Ÿ Provided by Mary Boldan, Mary Moisand and Donna Siemro, University of Illinois Extension Master Gardeners. Send questions to Ask a Master Gardener, c/o Friendship Park Conservatory, 395 W. Algonquin Road, Des Plaines, IL 60016, (847) 298-3502 or via e-mail to cookcountymg.com@gmail.com.