As the summer heat subsides and the first hints of fall appear in the northern hemisphere, it is time to harvest the grapes! Whether you’re growing your own batch, doing your research before heading to a vineyard, or just a huge fan of seasonal fruit, read on to learn how to harvest grapes, when, and what to look for throughout the process.
When to Harvest Grapes: Timing and Other Measurable Factors
Generally, grape season is from August to November in the northern hemisphere and March to August in the southern hemisphere. The period for harvesting grapes is usually between thirty and seventy days after the fruit set. The timing can also be influenced by the length of the growing season, the variety of grape, the desired flavor profile, and the crop load.
You should pick your grapes on a hot day with plenty of sun exposure to prevent surface moisture that complicates grape storage. Sun-harvested grapes will also have the highest sugar content.
The intended purpose of the grapes, or whether they are destined to become wine, raisins, jelly, or eaten straight, should also be considered when determining your harvest timing. Raisin grapes should be left on the vine for an additional three to four days to increase the sugar content, while jam grapes can be harvested three to four days early because they will be mixed with sugar later on. Grapes intended to be eaten plain or used for wine are the most finicky, so it is important to learn how to harvest grapes with the correct timeline in mind. Learn more about wine grapes from our guide!
If the grapes are meant to become wine, the type of wine you intend to produce also determines the timeline of the grape harvest. Sparking wines are made from more acidic grapes, which are picked earlier in the season. White wine grapes are the next to be picked, and then finally grapes harvested for red wines at the end of the season in October or even November.
Many say that taste is the most reliable method to practice when learning how to harvest grapes. Grapes should be sweet, not tart, and firm. Make sure the grapes are not too acidic, and not too tannic, and that they are neither vegetal nor sickly sweet. If you are growing more than one variety, be sure to try them all to ensure that they are ripe, and familiarize yourself with the variations in their natural taste.
Sample your grapes three to four weeks prior to the harvest date and continue to taste them until they reach maturity. Be sure to try grapes from different areas on the vine, included shaded and in full sunlight, to ensure that the whole crop is ready.
When deciding how to harvest grapes, observe the changes in color. White variety grapes change color from green to yellow and red variety grapes change color from red to purple when they are nearing readiness. However, be sure to avoid picking the grapes as soon as they are the correct color, as the change in hue occurs one to three weeks before full ripeness–and sweetness!
The color change is due to an increase in sugars coinciding with a decrease in acids, which occurs when the grapes are ripe. You can measure the sugar content, or BRIX, of your grapes using a refractometer, which can be found on Amazon, if the grapes are intended for wine.
When pressing the grapes on the vine, they should feel plump, thick, and saturated with juice. If they have started to shrivel, the grapes have gone beyond ripeness, whereas if they have no give when you squeeze them, they are not yet ready for harvest.
Seed color is another helpful tool to measure ripeness when you’re learning how to harvest grapes. Grape seeds–for grapes that are not seedless–indicate ripeness when they turn from white to tan to brown. Learn more about grape seeds from our guide on how to grow grapes from seed!
Things to Look Out For When Learning How to Harvest Grapes
Wildlife and Pests
Ripe grapes attract squirrels, raccoons, and birds. Be sure to harvest the grapes before the critters get to them–but not too soon before!
Frost and Grapes
Grapes may actually sweeten if they undergo a light frost after ripening, but extensive freezing will damage the crop, so it’s best to harvest the grapes before this occurs.
How to Harvest Grapes
Hand-Picking vs. Machine Picking
When deciding how to harvest grapes, you’ll have to choose between hand picking and machine picking. Commercially produced grapes are typically harvested using machines, while home grown grapes are harvested by hand with garden pruners or scissors. While machine picking is more efficient, the more traditional method of hand picking ensures the highest quality.
Machine harvesting is a relatively new method, introduced in the 1960s. Machine harvesting vastly increases the scope of harvesting but is usually only feasible for commercial purposes. The machine travels row by row along the vines, shaking the grapes off the vines to be chilled more quickly.
It is possible use the machines day and night, but machines are less discerning than relying on hand-picking. They are also difficult to use in uneven terrain. Still, modern machines can be calibrated to pick only ripe and undamaged fruit, so with improvements in technology, this method will continue to increase in popularity.
Picking by Hand
If you’re wondering how to harvest grapes by hand, start at the top of the cluster stem, which you can locate at the point where the stem meets the large vine. Always use your scissors or pruners rather than breaking or tearing off clusters, which can damage the grapes and the entire vine. Carefully place the grapes in a bucket or basket to keep your hands free for cutting.
Be sure to pick only the best bunches, avoiding sun damage and vine rot.
Crushing and De-stemming
Grapes destined for use in wine or jams are first de-stemmed and then gently split to get their juices flowing at the right consistency and temperature for optimal flavor.
Packing and Storage
Grapes can be stored in a temperature and humidity-controlled cellar for up to six weeks in dry, four-quart cardboard boxes lined with straw to cushion the grapes. Be sure to secure the cellar against any unwanted odors, as well as rodents and insects.
Small batches of grapes can also be frozen at 0 degrees Celsius (or 32 degrees Fahrenheit) for between five and seven weeks without damage. For smaller batches intended to be eaten directly, you can place the grapes in your personal freezer, ideally set at 90 percent humidity. The vegetable drawer of your refrigerator should suffice if you place the grapes in a sealable plastic bag.
Frequently Asked Questions About How to Harvest Grapes
How to harvest grapes with the proper tools
Why might uneven ripening of the crop occur?
Uneven ripening refers to when some grapes on the vine stay sour, hard, and in their original color, while others ripen and darken in color as they should. Too many grape clusters on the vine, also referred to as over-cropping, might cause uneven ripening. Potassium deficiency, drought, and warmer than usual temperatures can all also cause uneven ripening.
What are some common grape diseases to look out for?
Black rot causes hard, shriveled, and mummified grapes and can be prevented with copper fungicide applied in the spring.
Botrytis bunch causes grapes to be coated with fluffy gray-brown fungal spores. To prevent this, ensure good air circulation around the grapes.
Anthracnose causes sunken, ringed spots on grapes, and powdery mildew produces discolored fruit. Both can be prevented with lime sulfur in the spring.
Enjoy Grape Harvest Season!
Now that you’ve learned all about how to harvest grapes, including what to look out for, timing, and various sensory tests to determine ripeness, enjoy your grapes in homemade jams or straight from the vine, and check out our guide on grapes for further growing inspiration!