Thank you for your question about when to harvest your grapes.  The exact time can vary depending on cultivar, weather, and microclimates in your area. The OSU Extension publication entitled, “Growing table grapes” provides the following tips about when to harvest: 

There are several signs that can help you judge the ripeness of your grapes.

 ·      The color of ripe grapes varies with cultivar. Once you become familiar with a particular variety, color can help you judge when the grapes are getting close to maturity. (see photos in appendix end of publication)

·      The stem that supports the cluster changes from green to brown as the cluster reaches maturity.

·      The seeds of seeded grapes darken as the berry matures. The best way to judge whether table grapes are ripe is to taste them.  Taste berries at the tip of the cluster.  These are the last to ripen.

 Source: Growing table grapes https://catalog.extension.oregonstate.edu/ec1639

 If you need additional information, you can call the Deschutes County OSU Extension office in Redmond at<personal data hidden>.  You can ask to speak with Amy Jo Detweiler or Toni Stephan, members of the Horticulture Staff.  Both Amy Jo and Toni welcome your home garden questions.