This is the time of year, especially when we have fabulous weather like this, when growers ask me about getting a jump on the pruning season before winter sets in. Please let me say now, unequivocally- this is a bad idea.

At this point in the season, grapevines are in the middle of the active process of acclimation to cold temperatures that are expected in winter. While vines that have dropped their leaves look dormant, they are still busy apportioning nutrients and water into storage tissues and intracellular spaces which allows plant cells to freeze without bursting and causing tissue damage. Pruning at this time of the year stimulates callus tissue formation and other biological processes that slow acclimation and may even lead to deacclimation- the process in which a plant actively reduces its cold hardiness in preparation to commence growth for a new season. You don’t want that just before winter sets in.

It is best to wait until vines are fully dormant before winter pruning. When is that? It’s a moving target, but you can typically assume that to occur after the holidays, so count on starting pruning in 2027. Acclimation and cold hardiness are affected by numerous factors, including cultivar (#1 factor); weather, especially late fall (warm weather after harvest, like we have now, slows acclimation and reduces cold hardiness); crop load the fall before (more crop = longer to acclimate; nutrition and water status; disease incidence; and several other factors.

NEWA has a trial grape cold hardiness model that’s worth messing around with but is better at estimating whether damaged occurred after a cold event is experienced.

The take-home / TLDR message here is to hold off on pruning grapes until the new year.

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Terence Bradshaw (he/him)
Associate Professor, Specialty Crops

Chair, Dept of Agriculture, Landscape, and Environment

Interim Chair, Dept of Animal and Veterinary Sciences

Director, Horticulture Research and Education Center
College of Agriculture and Life Sciences

University of Vermont
117/210 – Jeffords Hall | 63 Carrigan Dr
Burlington, VT 05405

(802) 922-2591 | tbradsha
https://go.uvm.edu/alebradshaw

UVM Commercial Horticulture | UVM Fruit Blog

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