What to Do When Your Grapes Aren't Ripening
If you're waiting for your grapes to ripen and they're still green, it's possible that they are simply a green grape variety.
If they really are not ripening, the first culprit is likely a lack of sun. But remember: Some grape cultivars ripen later than others, so it might just be the expected timeline for your vine.
Further, make sure the grape varieties (Vitis spp.) you are growing are recommended for your region.
Do grapes ripen off the vine?
If you harvest your grapes before they're fully ripe, they will not ripen or sweeten further off the vine. So this guide will help you troubleshoot what you can do while they're still on the vine.
Choose the right grape varieties for your area to ensure healthy growth and a harvest within your location's growing season.
Provide Sun to the Vines
Grapes need sun to ripen. Rather, to clarify, the vines need sun—the fruit itself doesn't benefit from direct sun. It's the leaves that manufacture the natural sugars that are then transferred to the fruit.
Prune Away Some Leaves and Thin the Vines
So the first order of business is to ensure that more light reaches more leaves in the vine, so your pruning shears will be your best friend during the summer months when grapevines typically put on lush foliage growth.
Prune off some leaves and thin the vines on a regular basis, because you are growing a vine, not a thicket. This will also help direct the vine's energy toward development of the fruit rather than on leafy growth.
Choose Appropriate Varieties
Some grape varieties need a nice, long season to ripen. If you live in a cold climate with a relatively short growing season and you've planted a cultivar that requires more time to ripen, the fruit will not ripen well. It will have a lower sugar content when you harvest it, and the flavor will suffer.
In addition, a short growing season may mean that some varieties won't mature properly, which can result in vine damage in winter.
Consider Replacing Your Grapes with a More Appropriate Variety
If you inherited a grapevine and therefore don't know its variety, you may want to replace it if it's not thriving in your yard. Grapevines grow quickly, producing fruit in just three years.
If you want to replace your vine, consult your local university extension office for recommendations regarding varieties.
The best test for knowing whether or not grapes are ripe is always a taste test! Just be sure to pluck a grape from the end of a bunch, because it's the ends that ripen last.
Know the Signs of Ripening
Since grapes will not ripen off the vine, it's important to recognize when they are mature.
Color Is Not a Clear Indicator of Ripeness
The color of the fruit is not a clear indication of ripeness, but it does tell you something—especially as you get more familiar with your vines. At this point, you will recognize a subtle color change. For example, they may change from a green color to either blue, red or white, depending on the variety. But a color change usually does not indicate full ripeness.
Berries Should Plump and Soften
Watch for that whitish coating to appear and for the berries to plump up and soften. The stem should still be strongly attached to the vine.
The Best Test Is a Taste Test
But the best test is always a taste test! Pluck a grape from the end of a bunch, because it's the ends that ripen last.
What You Can Do with Unripe Grapes
If your grapes just won't ripen, you can harvest them anyway and try some of these applications:
- Prepare the grapes by coating them with an egg white and sugar mixture for a tasty treat.
- Add them to salads, soups, stews or other dishes that may be a bit too savory or sweet to help inject some much-needed sourness and acidity.
- Juice them to make verjus, which can be then used to flavor baked goods like pies and tarts, mixed into drinks to make delightfully sour cocktails, incorporated into salad dressings or utilized as a marinade for fish.
I garden in the Pacific North west, previously Hawaii where I had an avocado orchard. I have a Master Gardeners certificate here in Eugene, Oregon.