![grape clusters grape clusters](https://i.etsystatic.com/13850829/r/il/f33a4f/3208998718/il_300x300.3208998718_lfk0.jpg)
![grape clusters grape clusters](https://thumbs.dreamstime.com/b/grape-cluster-leaves-white-background-42940490.jpg)
Stage III is the ripening period when sugars rapidly accumulate and berries soften. The end of Stage II is characterized by skin color change, indicating the initiation of fruit ripening, or veraison. For example, Pinot gris has a shorter Stage II than does Cabernet franc (Figure 2). This stage can be identified when seeds can no longer be cut with a sharp knife and last 1–3 weeks depending on the variety. This is the stage when the seeds are starting to mature (i.e., changing in color and hardness). Stage II is often described as a "lag-phase," a temporary reduction in berry growth. The duration of this stage is dependent on the grape variety and lasts between 4 to 10 weeks. Seeds are soft and green, and berries are hard, accumulating mainly organic acids (tartrate and malate), but no sugar. Stage I corresponds to a phase of cell division that results in a fast increase in berry size and weight. The phase of cell division (Stage I) is followed by a phase of cell expansion (Stage III) with an intermediate phase (Stage II) of a reduced growth called "lag-phase." Stage I
![grape clusters grape clusters](https://img.freepik.com/premium-photo/the-hands-of-a-woman-and-a-man-push-the-leaves-of-the-vine-apart-and-reveal-clusters-of-blue-grapes_471801-2362.jpg)
After bloom (flowering) and fruit set, initial berry growth is associated with a rapid cell division and a subsequent cell expansion. Grape berry is a fleshy fruit that grows in size and weight during the season following an S-shaped or double sigmoid curve pattern that can be divided into three different stages (Figure 1). Further, vintners want to know ahead of time how much fermentation tank space is needed. Growers need to know the quantity of grapes they produce, as well as whether vines are balanced enough (i.e., not over-cropped or undercropped) to produce quality fruit and healthy vines. CE is the practice of predicting as accurately as possible the quantity of grapes that will be harvested. This fact sheet assists growers with that endeavor by providing tools to reduce yield and quality variability, which can be achieved through crop estimation (CE). Therefore, future economic survival and success of grape and wine industries are dependent on our ability to understand and take this variability into account and strive to improve fruit quality. In addition, climate change (such as increased heat accumulation and rainy events) is predicted to increase this variability. Long-term sustainable production of grapes for wine making is increasingly tied to a clear and accurate knowledge of vineyard conditions, which often are variable due to inconsistent weather from season to season, especially in the eastern United States.