Although wine grapes don’t need much water during the season, they need to drink frequently and at key times, says Dr. Markus Keller, viticulturist for Washington State University.
The following are average amounts of water that grapevines use during growth stages.
• Bud break to bloom—uses less than 5% of its total requirement, equivalent to less than 1 inch of water.
• Bloom to fruit set—uses 15% or 2 to 4 inches
• Fruit set to veraison—uses 60% or 6 to 12 inches
• Veraison to harvest—uses 20% or 2 to 5 inches