Grapes must be harvested at the right stage of maturity to ensure high quality. There are several indicators of grape maturity. Berry color, size, sweetness, and flavor are the most useful indicators.
Depending on the cultivar, berry color changes from green to blue, red, or white as the grapes approach maturity. Color alone, however, should not be the sole basis for harvesting grapes. Berries of many cultivars change color long before they are fully ripe. At maturity, individual berries are full size and slightly less firm to the touch. As a final test, taste a few grapes for sweetness when berry size and color indicate the fruit is approaching maturity. Harvest grape clusters when the berries are sweet.
When harvesting grapes, remove clusters with a knife or hand shears. Sound grapes can be stored in perforated plastic bags in the refrigerator for up to two months.
Uneven ripening of the berries within a cluster is sometimes a problem. Possible causes include overcropping (too many grape clusters on the vine), potassium deficiency, moisture stress, and 2,4-D damage. Overcropping is the most common cause for home gardeners.
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on August 19, 2016. The information contained within may not be the most current and accurate depending on when it is accessed.