For best grape flavor, allow concord grapes to fully ripen before harvesting

Bob Dluzen
The Detroit News

One common mistake gardeners make when harvesting their concord grapes is picking them too early.

While early harvested grapes are still usable for grape jelly, grape juice, wine or other recipes, the intense grapey flavor will be greatly reduced when picked too early.

Beating the birds to the fruit before they eat them all is not a good way of knowing when to harvest.  Although the grapes may look purple, they would be far from being fully ripe. Birds always start feeding on grapes much earlier than full flavor.

Birds began to go after the grapes about three weeks ago, early in September. At that time, the grapes were quite sour and had very little of that wonderful intense concord flavor.

To help you decide when to pick your concord grapes, watch for a few clues.

Keep an eye on your grapes so you will become familiar with how they look. Observe the color of the skin. Try to notice how dark the color is and note the subtle change in color over time.  As concord grapes reach maturity, skin color will get noticeably darker. Also the shininess of the surface subtly changes.

Observe the changes in the color of the grape skins and amount of bloom on the surface.

While looking at the skin, check the amount of bloom that is present on the surface. Bloom is a natural white powdery coating that forms on the surface of grapes. As ripening nears, there will be an apparent increase in the density of the bloom.

Give your grapes a squeeze from time to time and note the firmness. Unripe grapes will stay quite firm while developing.  Mature, fully ripe grapes will become softer fairly quickly.

Cut open some grapes and check the seeds. Seeds will turn from green to brown as ripening time approaches.

Cut open a few grapes and look for the seeds changing from greenish to a more brownish color.

Leaves can provide a clue too. Leaves are responsible for producing sugars that sweeten the grapes. As leaves begin to lose color and turn brown, grapes will stop ripening because no more sugar is being added. All the sugar that the vines can put into the grapes will have peaked.

These grapes leaves are completely green and are still producing more sugar for the grapes.

Unless you have had experience growing grapes, your own taste is not necessarily the best indicator either. It's easy to get fooled into picking grapes too early as the grapes begin to ripen. This is where some patience is needed if you want to enjoy the full concord grape flavor. 

Of course, if you prefer the tart flavor of partially ripened grapes, by all means harvest and enjoy them. 

Keep in mind that partially ripened grapes will have less natural sugar and you will have to add more sugar to make up the difference when making wine for example. Also your grape jelly won’t have the full-bodied concord grape flavor that most people enjoy.

When deciding when to pick my concord grapes, I look for all the indicators: darker skin color, thicker bloom, softer fruit, brown seeds and fading leaves. If you follow these clues you’ll be able to enjoy the full flavor of your delicious concord grapes.