I’ve received reports from several growers about unexpected dieback in cold-hardy hybrids like Marquette, St. Pepin, and Prairie Star. In many cases, vines appeared healthy during winter pruning—green tissue, no visible damage—but later failed to push growth or only produced shoots from the base.

While I can’t say for certain what’s behind this, I suspect the issue might be root damage rather than traditional above-ground cold injury. I’ve been tracking bud cold hardiness this winter using the NEWA Grape Bud Cold Hardiness Model (link), and temperatures never dropped below the predicted hardiness levels. At our research vineyard at the West Madison Agricultural Research Station, we observed no winter injury to the vines.

This is definitely unusual. One possible explanation is the lack of snow cover during the coldest parts of winter, which may have left roots exposed and vulnerable to damage. Snow acts as a natural insulator, protecting the soil and roots from extreme cold temperatures. Without this insulation, soil temperatures can drop significantly, leading to root injury. 

Additionally, we don’t know much about root cold tolerance, and root distribution in the soil might also affect the severity of the damage. Some cultivars might have more superficial root systems that would be more exposed to cold damage than those from cultivars with deeper root systems. This could explain why younger vines and fruit trees with smaller and more superficial root systems would experience more damage in a situation like this.

If you’re seeing symptoms like this, I recommend holding off on removing vines right away—some may still push growth from the base. And if you’re willing to share your observations, I’d appreciate it as we try to better understand what happened this year.

This article was posted in Grapes and tagged Amaya Atucha, dieback, Grapes, vine dieback.