Veraison in viticulture refers to a stage of grape development and signals the beginning of the ripening process of the grapes. At that time grape berries start to change their color from green to yellow or red depending on the grape varieties. During the veraison stage, grape berries start to soften and enlarge due to a sugar increase in the berries. Not all berries on one cluster onset the veraison at the same time. Berries and cluster that are most exposed to warmth undergo veraison first, while berries and clusters closer to the trunk and in shades of the canopy undergoing it last.

In the Northern Hemisphere, veraison normally occurs at the end of July and into August, while in the Southern Hemisphere between the end of January into February.

This is also a perfect time for a grape thinning also known as crop thinning, cluster removal, etc. It is used to achieve the desired yield and quality of the grape and thus the wine.

We are sharing two videos on the veraison and crop thinning topic. In the first video winemaker, John Hawley from Hawley Winery discusses veraison, berry development, and crop thinning practice in his Zinfandel vineyard. While in the second video Assistant Winemaker Ronald Du Preez from Jordan Vineyard and Winery discusses the importance of veraison thinning.

  • Video by John Hawley, from Hawley Winery

  • Video by Ronald Du Preez, from Jordan Vineyard&Winery

Grape-growers do you practice crop thinning in your vineyard? Let us know in a comment below!

Source:
In the Vineyard: Veraison and Crop Thinning, Hawley Winery (YouTube)
Veraison thinning: removing grape clusters after color change (The Journey Blog 8.24.10), Jordan Vineyard & Winery (YouTube)
Annual growth cycle of grapevines, Wikipedia