UP CLOSE: Fruit Set

The pollination of little grapevine flowers almost immediately leads to a phase called “set,” where the fruit actually begins to appear on the cluster in the form of very small grape seeds, and berries to protect them.

This stage is important for wine production because it determines the potential crop yield. As anywhere in nature, not every flower on the vine will be fertilized; unfertilized flowers will eventually die and fall off the vine. On average, about thirty percent of flowers on a vine will be fertilized.

wine grapes fruit set
A good set is determined by many factors, especially the general health of the vine and the climate. Low humidity, hot temperatures, and lack of water can drastically reduce the number of flowers that get fertilized. “Shatter,” or abnormal fruit set, can occur is there is an imbalance of nutrients or carbohydrates. Some clusters may have berries of various sizes, which can lead to winemaking problems since the “skin to pulp ratio” will vary.

Set allows the vineyard team to determine potentially how large the crop that year is going to be, which affects many subsequent farming decisions. By counting clusters on a specific group of vines and measuring their weights, a reliable yield estimate can be formed. Wine growers can then consider the necessary laborers needed during harvest, potential vineyard returns, and grape load sizes.

wine grape cluster set