When Are Grapes Ripe? How to Tell, How to Pick and How to Keep Them

Grapes stop developing the moment you cut them

Unlike a pear or a peach, a grape does not continue to sweeten off the vine. Whatever sugar is in the berry when you cut the bunch is all it will ever have. Picking a week early therefore costs you the best week of the whole season, and there is no way to recover it on the windowsill.

The corresponding risk is leaving fruit too long, when the skins soften, wasps find it and rot spreads bunch to bunch. In practice the good window is around one to two weeks wide, so the skill is in reading the signs rather than following a calendar.

Color change is the start of ripening, not the end

The stage where berries stop swelling, soften, and change color is the moment the vine switches from growing fruit to sweetening it. Dark grapes go from green to red to their final color; pale grapes turn from a hard grass green to a translucent yellow-green with a golden cast. Sugar then climbs steadily for another four to six weeks.

This is why color by itself is such a poor guide. A dark grape reaches full color weeks before it reaches full sugar, and a bunch that looks perfect can taste sharp and thin. Wait a minimum of four weeks after the color finishes changing before you even start tasting seriously.

Test the bunch properly

One berry off the top of a bunch tells you almost nothing. Berries ripen unevenly within a bunch, with the shoulders always ahead of the tip, and bunches on the sunny side of the vine run ahead of those in shade. Test in a way that accounts for both.

1. Taste from the bottom of the bunch Pull a berry from the very tip, the last to ripen. If that one is sweet, the whole bunch is ready. A sweet berry from the shoulder proves nothing.
2. Check the seeds Bite or squeeze a berry open. Green seeds mean wait; hard brown seeds mean the berry has finished developing. This is the most reliable single check on a seeded vine.
3. Look at the stalk Follow the bunch stem back to the shoot. As the bunch finishes ripening that stem turns brown and woody from the shoot outward. A bright green stem means more time.
4. Sample by position, not by vine Test one bunch in full sun and one in shade. Pick the sunny ones first and leave the shaded ones another week or two rather than stripping the vine in one go.
5. Repeat every three days Once the first bunch tastes close, taste again every couple of days. The last week of ripening changes the flavor very quickly.

If a hard rain is forecast when the fruit is nearly ready, pick. Water taken up quickly at that stage splits the skins, and split berries mold within a day or two and take their neighbors with them.

Cutting and handling

Always cut the bunch off with scissors or pruners, holding it by the stalk. Pulling a bunch tears the shoot bark and drops berries, and handling the berries themselves rubs off the waxy bloom that protects the skin and keeps the fruit fresh for far longer.

Cut in the cool of the morning, once any dew has dried. Warm fruit picked in the afternoon carries field heat that shortens its keeping life considerably. Lay bunches in a single layer in a shallow tray rather than piling them into a bucket; the weight of a few pounds of grapes crushes the bottom layer.

Sort as you go. Snip out any split, shriveled or moldy berries before the bunches go into storage, because one rotting berry will infect the bunch around it within days.

Keeping the crop

Unwashed bunches in a shallow container keep two to three weeks at 32 to 36F (0 to 2C) with high humidity. Wash only just before eating: water on the skins removes the bloom and starts rot. Grapes also absorb strong odors, so keep them away from onions and anything heavily scented.

For longer keeping, grapes freeze well loose on a tray and then bagged, though they go soft when thawed and are best used from frozen. Juice and jelly are the usual routes for a glut, and slightly overripe fruit is better for both than for eating fresh.

Do not store grapes in a sealed bag. Trapped moisture condenses on the skins and mold follows quickly. A container with the lid resting loose works far better.

Record the harvest, not just the date

Write down the first and last picking dates, the total weight, and a plain note on flavor. Weight against bunch count is the number that matters: if you kept sixty bunches and the fruit was mediocre, the following winter's pruning and the summer's bunch thinning both have a clear target to aim at.

Also note which vine and which part of the trellis ripened first. Over a few years that map of your own site tells you where to put the fruit you most want ripe, and where to expect to be picking a fortnight later.