Hello,

Thanks for reaching out with your grape questions and sharing the cultivars.

There is not a set date or month when grapes or any other fruit or vegetable ripens, as weather can always influence things, as well as the cultural care of plants. The easiest way to determine when to harvest is by taste, according to the Colorado State University Extension.

Oregon State University has more detailed information that may be helpful as well:

"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.

-- 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.

Grapes become sweeter and less acid as they mature. The characteristic aroma and flavor of a cultivar develops relatively late in the ripening process."

In doing our research, we found that Niagara grapes are greenish white when ripe, while the Canadice grapes are red when ripe.

If you have additional questions, please let us know.

Enjoy your grapes!