Early Hedging for Healthier Canopies and Better Ripening in Cool Climates

By Esmaeil Nasrollahiazar

Canopy management is a critical component of successful viticulture, especially in cool climate regions such as northwest Michigan. Among the various practices involved in canopy management, shoot hedging, or "topping," plays a key role in optimizing the photosynthesis of grapevines in supporting fruit ripening. While traditional approaches often recommend delaying hedging until later in the growing season, recent research by Michigan State University (MSU) in collaboration with industry partners suggest early hedging can provide significant advantages in cool climate vineyards where the growing season is short and ripening windows are limited.

In the past, canopy hedging was often postponed until the shoot tips had grown well above the top wire and had even begun to bend back into the canopy. At that stage, hedging involved removing a large portion of the canopy. Research by the Department of Horticulture at MSU showed that such extensive removal negatively impacted photosynthesis and reduced carbohydrate allocation to the fruit. Instead, the new approach is to hedge earlier when the growing shoot tips are just reaching the top wire. This minimal removal of vegetative growth provides two key benefits:

1. It preserves a greater portion of the photosynthetically active leaf area.
2. It stimulates the development of lateral shoots, which later become an important source of carbohydrates during fruit ripening, starting at veraison.

This has been demonstrated in trials held at Lemon Creek Winery and Brys Estate by Michigan State University Extension specialist and professor Paolo Sabbatini and his team. The treatment resulted in an increase of up to 2 degrees Brix at harvest. In many cool-climate vineyards trained to vertical shoot positioning systems, shoot growth continues vigorously well past the top wire. If left unmanaged, these shoots can shade the fruiting zone, reduce airflow and suppress the productivity of interior canopy leaves. A common recommendation is to hedge once shoots begin to bend or fall over the top wire. However, this approach can result in the removal of the youngest and most photosynthetically active leaves, the exact leaves needed during the critical ripening period.