INTRODUCTION: According to various sources on the internet, snipping back the tips of raspberry canes (a.k.a. “tip-pruning) may encourage secondary or lateral branches to grow from the main cane, thereby increasing raspberry yield. Furthermore, some say that the berries on these lateral branches will be bigger bigger than berries grown from the main cane on un-tip-pruned raspberry canes. However, this advice on tipping raspberry branches is not uniformly rendered. Many reputable gardeners make no mention of tip-pruning. The purpose of the present study is to investigate the effects of tip-pruning raspberry canes.
METHODS: Willamette variety raspberry canes were used in this experiment. A single pot of Willamette raspberries was grown on a USDA Hardiness Zone 8b apartment balcony for over a year. After pruning out old growth from the prior year, three canes were available for the study. Two similar-in-size dominant branches were determined to be used in this study; the third, smaller cane was not included. The terminal 6-8 inches of one cane was removed with pruners in March. The other cane was left un-tipped. Raspberry yields were counted in June.
RESULTS: The tip-pruned cane yielded 87 raspberries, and the un-tip-pruned cane yielded 80 raspberries. Thus, there was an 9% increase in productivity of the tip-pruned cane. Counting only raspberries along the terminal 20 cm of each cane, the tip-pruned cane yielded 14 raspberries, whereas the un-tip-pruned cane yielded 6 raspberries on the terminal 20 cm of cane. The productivity of the terminal 20 cm of the tip-pruned cane was 230% greater than that of the un-tip-pruned cane.
CONCLUSIONS: The authors of this study conclude that tip-pruning may increase raspberry production by as much as 9%. However, the authors note that the sample size in this study (N=2) is lacking, and further research is needed to confirm the results of this study. Furthermore, the current study cannot determine if tip-pruning affected the taste of the raspberries, as the raspberry grower (N.E.) combined the harvested raspberries in single bowl before consuming them. He reports that the raspberries tasted “delicious!,” but more research is needed.
Acknowledgments: The authors would like to thank the person who left a potted raspberry bush out on the curb for free in the summer of 2020.