Do Seedless Grapes Ripen After You Pick Them?

Taste Test

• The most obvious test for picking ripened grapes is the taste test. Choose a bunch that you are considering picking, and test one of its grapes. If the grape is sour or has a hardened skin, it is likely not ripe just yet. Return to the vine in a week and repeat the test. If your vines are overgrown, you may have many grape bunches that do not ripen before the season ends. Consult a guide to properly prune your vines to prevent overgrowth in the future.

Size

• Ripened grapes should be between a nickel and a quarter in size, depending on the variety. Unripened grapes will be substantially smaller and will often sit on a bunch in such a way that none of the grapes are touching each other. An unripened grape will contain very little sugar and thus be bitter and difficult to chew.

Color

• Unripened grapes will appear very opaque, which means very little light passes through them. Ripened grapes begin to take on a shine, appear more transparent and may have liquid visible inside of them. Knowing what color the ripened grape bunches of your particular variety will have can help you make an assessment as to the ripeness of a particular grape bunch.

Season

• Most grapes ripen after Labor Day. Nearly all grapes ripen toward the end of the season. If you are looking at grape bunches before late August, you are likely looking at unripened grapes. Knowing when your particular variety ripens can help you decide when you should begin taste-testing grapes from your vine to ascertain whether they are ripe. Consulting your local university extension's horticultural department can be helpful.