Following spring hailstorms, many growers throughout Wisconsin are observing vegetative side-shoots on uprights. In many cases the uprights that exhibit later shoots also have an apical bud that is very delayed in development, and it is not clear whether that apical bud will pull through and bloom. Scouting beds will be critical to estimate the percentage of uprights with apical buds either damaged or not developing. If there is a significant amount of damage to apical buds, which will result in yield reduction, and in addition there is a lot of side shoots, then fertilizer application will have to be reduced as well. If growers do not adjust fertilizer application, then those side shoots will grow vigorously and will not set flowers for the spring of 2023. The only tool we have to control the growth of those lateral shoots is to reduce fertilizer application.
Identifying vegetative side-shoots
Vegetative side-shoots are your cranberry plant’s response to a damaged apical meristem. The meristem may be damaged in a variety of ways (spring hail, tipworm damage, etc), but no matter what the cause, the plant responds by producing new shoots from dormant vegetative buds located immediately below the apical bud.
Managing vegetative side-shoots
Vegetative side shoots should be thought of both for their impact on the current season’s crop, and on the following season’s crop.
Current season: If the apical meristem was damaged but not killed, the vegetative side shoots will be competing with the fruit for nutrition. This can result in fewer or smaller fruit. If the apical meristem was killed, there will be no fruit for the vegetative side-shoots to compete with, but this means your vegetative side shoots will be even more likely to overgrow.
Next season: This is the main arena where your management will have an impact. Vegetative shoots have a tendency to overgrow, especially when they receive ample nutrition. Because fruit demands nutrients, uprights with fruit necessarily “end” vegetative growth to direct nutrients to the fruit, and this allows next year’s bud to form. When there is not fruit limiting the nutrients the vegetative shoot can receive, it can continue to grow, and fail to set next year’s bud.
To prevent your vegetative side shoots from overgrowing, reduce the fertilizer you had planned to supply. On a bed-by-bed basis, check the % of uprights showing vegetative side-shoots. If you have a bed with 10% of uprights with side-shoots, reduce your fertilizer (N and P and K) by 10%. If 50% of uprights are showing vegetative side-shoots, reduce your fertilizer by 50%. Check each bed and make each bed’s fertilizer rate decision based on conditions you see when scouting. Use what you see, and adjust this advice if you see signs of deficiency, or reduce your fertilizer further if you are still seeing overgrowth.
After blossom will be a critical period for managing your vegetative side-shoots to prevent yield reductions for 2023, so please reach out with any questions you have.This article was posted in Cranberry and tagged Allison Jonjak, Amaya Atucha, Cranberries, vegetative side shoots.