With the summer heat waning and the first signs of fall in the Northern Hemisphere, it's grape harvest time! Whether you're growing your variety, doing your research before heading to the vineyard, or are a big fan of seasonal fruits, read on to learn how, when, and how to harvest grapes.
- The time
Generally, the grape season is from August to November in the Northern Hemisphere and from March to August in the Southern Hemisphere. Grape picking time is usually between thirty and seventy days after fruiting. Timing can also be affected by the length of the growing season, grape variety, desired flavor, and crop weight. Grapes should be picked on a hot day with plenty of sun exposure to prevent surface moisture that complicates grape storage. Sun-harvested grapes also have the highest sugar content. The purpose of the grape, or whether it is destined to be wine, raisins, jelly, or eaten directly, must also be considered when determining the time of harvest. Raisin grapes must be left on the vine for three to four days to increase the sugar content, while jam grapes can be harvested three to four days earlier as they will be mixed with sugar later. Grapes that are used for eating or wine are the hardest, so it is important to know how to harvest grapes with the right schedule in mind. Learn more about wine grapes from our guide! If the grapes are to be made into wine, the type of wine you want to make also determines the time of the grape harvest. Sparkling wine is made from more acidic grapes picked early in the season. White wine grapes are to be picked, then finally the grapes for red wine are harvested at the end of the season in October or November.
- Taste
Many say bait is the most reliable way to practice when learning how to harvest grapes. Grapes should be sweet, not sour and ripe. 
Make sure the grapes are not too acidic, not too sour, and are not vegan and not sweet. If you grow more than one variety, try them all to make sure they are ripe, and to learn about the differences in their natural flavor. Taste your grapes three to four weeks before harvest time and continue tasting until they reach ripeness. Test grapes from different areas of the vine in both shade and full sun to make sure the entire crop is ready.
- Glance
When deciding to harvest grapes, pay attention to changes in color. White grapes change color from green to yellow, and red grapes change color from red to purple as they approach readiness. However, be sure to avoid picking the grapes when they are just the right color, as the color change occurs one to three weeks before full ripening – and sweetness. The change in color is due to an increase in sugars with a decrease in acid, which occurs as the grapes ripen. You can measure the sugar content, or Brix, of grapes with a refractometer, which can be found on Amazon, if the grapes are for wine.
- Feel
When squeezing the grapes on the vine, they should feel thick, plump, and saturated with juice. If the grapes begin to shrivel, the grapes are overripe, while if they do not soften when pressed, they are not yet ready for harvest.
- Seed color
Seed color is another useful tool for measuring ripeness when you're learning to harvest grapes. Grape seeds – for grapes that are not seedless – indicate ripeness when they turn from white to brown. 
- Things to look for when learning how to harvest grapes
- Wildlife and insects
Ripe grapes attract squirrels, raccoons, and birds. Be sure to harvest the grapes before the creatures arrive - but not too soon!
- Frost and grapes
Grapes can be really sweet if exposed to a light frost after ripening, but extensive freezing can damage the crop, so it's best to harvest grapes before this happens.
- How to harvest grapes
- Manual selection vs. automatic selection
When deciding how to harvest grapes, you have to choose between hand picking and machine picking. Commercially grown grapes are usually harvested using machines, while locally grown grapes are harvested by hand using shears or garden shears. While automated picking is more efficient, the more traditional method of manual picking ensures higher quality.
- Harvesting machine
Machine harvesting greatly increases the scope of the harvest but is generally only feasible for commercial purposes. The machine moves along the vines row by row, shaking the grapes off the vines to cool more quickly. Day and night machines can be used, but the machines are less intuitive than relying on manual picking. It is also difficult to use on uneven terrain. 
However, modern machines can only be calibrated to pick ripe and undamaged fruit, and as technology improves, this method will continue to grow in popularity.
- Pick up by hand
If you're wondering how to harvest grapes by hand, start at the top of the stem, which you can find at the point where the stem meets the main vine. Always use scissors or shears rather than breaking or tearing the clusters, which can damage the grapes and the entire vine. Carefully place the grapes in a bucket or basket to free your hands from slicing. To avoid sun damage and vine rot, be sure to choose only the best clusters.
- Crushing and de-derivation
Grapes intended for use in wine or jam are first stripped of stems and then slowly tinted to allow the juice to flow at the right consistency and temperature for optimal flavor.
- Packing and storage
Grapes can be stored in a temperature- and humidity-controlled cellar in dry, straw-lined four-quarters cardboard boxes to house the grapes for up to six weeks. Be sure to secure the basement against any unwanted odors as well as rodents and pests. Small batches of grapes can be frozen at 0°C (or 32°F) for five to seven weeks without spoilage. For small batches intended for direct consumption, you can store the grapes in your freezer, where the humidity is ideally set at 90 percent. The vegetable drawer in your refrigerator will suffice if you keep the grapes in a resealable plastic bag. 
Increasing The Quality of Grapevine
Several items have a significant effect on grapevine quality. Increasing the quality of your crop cause you to have a more and better crop.
- Primary and secondary metabolism
An important part of berries is their sugar content. Sugar is formed from carbon dioxide at the source (ripe leaves) and travels to the pods: berries, young leaves, roots/stems. The use of combination stress agents is essential because a plant's response cannot be predicted by its response to a single stress factor. Three parameters that will change in the coming years, namely carbon dioxide, temperature, and water availability, have been studied in two types of Tempranillo: the effects of carbon dioxide and temperature depend on the variety and culture. Photoadaptation is observed under long-term exposure to elevated carbon dioxide. The relationships between photosynthesis, carbohydrate metabolism, and the expression of sugar-related genes were studied in leaves with different lighting (east/west/sun/shade). Sugar recovered from the east, west, and sun. Shadow leaves accumulate starch and sugars, but the origin of these carbohydrates is unknown because the photosynthetic activity of these leaves is negligible. Carbon inputs and outputs must be taken into account to calculate the carbon balance. These parameters were measured in leaves under many conditions, but fruit respiration was rarely considered. Staphylococcal dyspnea during development. Tempranillo loses more carbon than Grenache. What is that (mostly?) in berries intended for wine production? Quantification and properties of secondary metabolites. The regulation of vital gene expression, characterization, and quantification of various metabolites are studied. 
- Germs
Grape stem diseases (Esca, Black Dead Arm, Eutypa, …) have been developing since sodium arsenic was banned in 2003. Yield loss can be up to 20%. Leaf metabolite imprinting was performed on two different copies. A clone and the year-dependent metabolic response have been demonstrated. Moreover, the comparison with the data obtained in Chardonnay did not allow the identification of metabolic fingerprints of Esca.
- Water use efficiency and dehydration
Grapes are often grown in drought-prone areas. The water use efficiency for producing given biomass can be defined at different scales and given different names: water use efficiency (WUE) or transpiration efficiency. The importance of these parameters lies in the relationship between water loss through the oral pores and carbon dioxide fixation. The organization of the mouth opening has been studied in different conditions and types. Several studies have been conducted to compare the variance in WUE between different, for example, by comparing isohydric (Grenache) and anisohydric (Syrah). Genetic diversity within cultures was studied using 13 Grenache genotypes (red and white) under field conditions over three seasons. They showed that three parameters (internal WUE, crop WUE, and 13C) are reliable indicators for the selection of drought-tolerant genotypes. 
While growing conditions are expected to be important for studying the effect of water availability on various physiological (environmental) parameters, it is also important to measure the deficits that may occur. The effect of container size on plant response to drought was studied by comparing several variables on plants grown in 7 or 20-liter pots. Before the drought, the number of leaves and average leaf area were similar among plants grown in containers of different sizes, but differences in the anatomy of woody vessels were identified. In addition, the response of plants to drought varies. But what needs to be clarified is the origin of the difference. Is the stress felt by the plant different or is the plant's physiology different at the onset of stress? In fact, differences in nutrient availability can lead to physiological differences. In addition to the importance of the developmental stage where drought stress occurs, the effect of stress velocity must also be considered. Compare rapidly developing dehydration with slowly developing dehydration in terms of stress response and recovery. They demonstrated that Grenache, which is usually described as a semi-isohydric variety, can behave as a semi-anisohydric variety when pressure is slowly applied. The non-proteinogenic amino acid β-aminobutyric acid (BABA) is a key defensive factor known for its ability to stimulate widespread disease resistance. It activates the expression of several defense-related genes such as PR protein genes and phytoalexin biosynthesis genes. The transcription factor (VvWRKY18) is identified as a Papa priming regulator. The use of specific organisms to passively control plant pathogens is a biological control strategy developed in vineyards. In addition to various seaweeds, Trichoderma spp. soil fungi are used and their mechanism of action is partially understood. 
- Mineral nutrition
Climate change also affects the mineral nutrition of grapes. If we take into account only the two main nutrients, potassium and nitrate, then a strong influence on the quality of the berries can be expected. As for potassium, its increase in berries is associated with a decrease in acidity, which is often a source of low-quality wine. Potassium flux in plants is affected by climate change and increases potassium concentration in berries. Nitrogen is involved in the growth, development, and synthesis of secondary aromatic metabolites. In addition, the nitrogen content of berries is important for the fermentation process. Nitrogen availability, absorption, and metabolism affect the nitrogen composition of berries. The effects of agro-climatic conditions on the nutrition of N. Producers and scientists face many challenges to deal with climate change. Since semi-arid regions are already under cultivation, increasing drought will not be fully countered by management practices such as irrigation or architectural forms. There is a need to exploit natural diversity and develop breeding strategies. Our understanding of the effects of abiotic stress due to climate change on different grape species has been recently revised. The class-dependent flexibility of heat waves must be studied because it is unpredictable from the response to other stresses. Regardless of stress, infection rate is increasing and effects on plant growth and yield have been observed. The cumulative effects of stress over the years is a challenge to deal with.