Ripening Of Grapes: When To Harvest Grapes

In my neck of the woods, the Pacific Northwest, it seems every other day a new winery pops up. Some of them make it and some of them don’t; the result not only of savvy marketing but the quality of the wine which directly correlates to the superiority of the grape. For the home gardener, growing grapevines may create a lovely shaded oasis or arbor, or an ornamental detail with the added bonus of edibility. But how do you know when to harvest grapes at the peak of their sweetness and optimum flavor? Read on for some grape harvest info.

When to Harvest Grapes

The precise time for picking grapes is dependent on the location, length of growing season, variety of grape, crop load and the intended use of the grape. Heavy crop loads take longer to mature. The optimum time for harvesting grapes will vary year to year as do environmental conditions — sometime after the berries turn color (veraison).

Commercial grape growers rely on more scientific methods to determine when to harvest the grapes such as precise pH levels and sugar contents (Brix) that are established with testing. The home grower may make use of the following to ascertain the ripening of grapes and proper harvest time:

Color – Harvesting grapes for use in jellies or wine making must occur at just the right stage of maturity for maximum sweetness. Grapes change color from green to blue, red or white, depending upon the variety. Color is one of the indicators of ripeness. However, it is not the most reliable indicator, as many varieties of grapes change color well prior to ripening. Still, when completely ripe, the whitish coating on the grapes becomes more evident and the seeds turn from green to brown.

Size – Size is another gauge of the ripening of grapes. When mature, the grapes are full size and a bit less firm to the touch.

Taste – Hands down, the best way to ascertain if your grapes are ripe enough to harvest is to taste them. Sample the grapes three to four weeks prior to the approximate harvest date and continue to taste the grapes as they mature. Try to take samples at the same time of day from a variety of areas on the vine.

Grapes, unlike other fruits, do not continue to ripen once off the vine, so it is important to keep tasting until the grapes are uniformly sweet. Sample from sun exposed areas as well as those that are shaded. Ripeness and color of grapes is not reliant upon direct sunlight, but rather the amount of light that reaches the grape foliage results in high quality fruit. It is the leaves of the grape that engender the sugars, which are then transferred to the fruit.

Additional Grape Harvest Info

Uneven ripening may occur due to too many grape clusters on the vine (over-cropping), potassium deficiency, drought or other environmental stressors. Warmer than normal weather is often the cause of uneven ripening, wherein some berries stay sour, hard and green while others ripen and darken in color normally.

Ripening berries are also extremely attractive to the birds. To protect the impending harvest, you may want to envelop the grape clusters in a brown bag tied to the cane or by netting the entire vine.

Once you have ascertained it is prime time for a grape harvest, simply remove the clusters with hand shears. Grapes can be stored at 32 F. (0 C.) with 85 percent relative humidity, in a perforated bag for up to two months.

Growing Grapes

The grape vine on the right is a Flame Seedless variety. It is growing on an east facing wall so it receives full sun in the morning and afternoon shade. A wooden trellis has been attached to the wall to give the grape something to climb.

This grape vine is planted in the grass where it only receives water from the sprinklers. The grass is trimmed up to the base of the grape vine, and care is taken to not ding the base of the vine when mowing the lawn. This vine has never been fertilized and yet grows vigorously.

Flame seedless grapes are ready to be picked in the middle of June and are an excellent variety for the Phoenix Arizona area.

Grapes grow very well in the lower desert, and are even grown commercially on a small scale. They do best with a fair amount of direct sun and regular water and can take the summer heat and winter cold. European grape varieties with high heat requirements are recommended.

The best grape varieties for the Phoenix area are in the European class (Vitis vinifera). Flame seedless grapes and Thompson seedless grapes are both in this class and these plants can be easily found for sale locally. The lower desert summer heat encourages these varieties to produce lots of sugar, creating a wonderfully sweet flavor. Interestingly, the heat also keeps some pigmented grapes from attaining full color, even when they are fully ripe. For example, flame seedless grapes stay green during the hottest months even when they are ready to eat. This requires one to perform taste tests for ripeness before picking them.

For a home gardener, a grape vine can be allowed to sprawl out on a trellis, fence, or wall and over time fruit will be produced. The grape enthusiast will want to maximize yield by pruning the vine. More information on grape vine pruning can be found at the following links. Both Flame Seedless and Thompson Seedless grapes should be cane pruned.

Heat Tolerance and Sun Exposure
Grape vines need at least a half day of direct sun to grow well and produce. They take the oven like heat of summer afternoons in the Phoenix area very well as long as they have adequate water.

Cold Tolerance
European grapes are hardy down to 5 degrees Fahrenheit so there are no concerns about frost damage in Phoenix Arizona. Grape vines are deciduous, so they will be leafless and dormant during winter.

Watering frequency
Grape vines do well on a grass watering schedule.

Watering method
Basin, flood, or sprinkler irrigation are suitable for grape vines.

Dig a hole at least twice the size of the rootball. At a minimum, make the hole 2 feet in diameter and 2 feet deep. Back fill the whole with the same native soil that was removed. It also is a good idea to finish with the hole an inch or two recessed so that a watering basin is formed. After planting, spread a thin layer of compost on top of the soil to help conserve moisture and to supply some nutrients. Do not fertilize the newly planted vine until it has been vigorously growing for a couple of months.

Fertilizing and Growth Rate
Regular applications of a balanced fertilizer during the growing season will benefit grape vines. Grape vines do not burn easily from fertilizer so chemical or organic fertilizers are suitable.

Grapes are propagated by cuttings and grafting and will not come true from seed.

Grape Leaf Skeletonizers, a type of catepillar, are a problem in the lower desert. I have just one grape vine so I originally controlled them through manual squishing. I did not find the caterpillars hairs to be a problem, although some people with more sensitive skin can find them irritating. I squish the caterpillar with bare hands using a finger tip rolling motion. I do avoid touching my face and eyes and other more sensitive skin until I have washed off my hands well. I must admit that the adult form of this caterpillar is quite beautiful, being an iridescent blue/purple colored moth.

I originally only had problems with grape leaf skeletonizers in fall months but now they are a problem through all the warm months. In fact, it is getting hard to keep up with them so I have started using a caterpillar killing spray called BT. It is one of the best options for the home garden containing a bacteria named Bacillus Thuringiensis (BT), which sticks to a plants leaves and gives the caterpillars a fatal tummy ache. Brand names for BT include Thuricide and Dipel. They are apparently safe for other creatures in the garden, even other insects, and are not hazardous to people. The only problem with BT is that it is photo degraded, so it does not last very long on the leaves, meaning it needs to be reapplied frequently. I apply it once a week when I see the catepillars and their damage begin, and keep at it until they have disappeared. BT is working very well and is much easier than squishing several hundred of them. To apply, I pour a half of a cap full of the mixture into a one quart spray bottle diluted with water and spray the entire bottle worth on my grape vine. The mixture smells very similar to stagnant pond water.

Another skeletonizer control option is a product called Spinosad, with has the brand names Entrust Naturalyte, and Monterey Garden Insect Spray . It is a chemical produced by soil microbes and is fatal to insects but not harmful to mammals. It also is photodegraded, so will not persist very long. In general, it appears to be slightly more toxic than BT because it persists in water and is more hazardous to other insects.

Carbaryl which has a brand name of Sevin is the harsher chemical alternative for killing grape leaf skeletonizers. It was invented in the 50's and has all of the toxicity one can typically expect of this type of product. Therefore, if used make sure the instructions are carefully followed and precautions are taken. It persists on the plants for quite some time, which means it will not need to be reapplied frequently.

There are evidently fly and wasp parasites of skeletonizers released by commercial growers in California. Also, a virus has been introduced into the skeletonizer population in California which has been generally successful in reducing their numbers. Neither the wasp or the virus control appear to be available to the home gardener here in Arizona.

Birds eating your grapes is another problem. I have tried to cover grape bunches with white paper lunch bags but this seems to interfere with the proper ripening of the fruit and encourages molds. Instead, do what the commercial growers do and cover you entire plant with a bird net. When the grapes are very green, the birds won't bother them but as soon as they start to get soft the fruit will need to be protected.

Links to more grape growing information

It's harvest time at the vineyards and wineries of Upstate New York

Gallery: Vines harvested at Toro Run Winery

It's coming about a week later than normal in much of New York state, but the annual harvest of grapes for the the state's more than 400 wineries is beginning. It should last this year into mid-October.

That signals one of the best times of the year to visit the vineyards, whether you're headed to the Finger Lakes, Thousand Islands, Lake Erie, Hudson Valley or other regions.

The vineyards will be buzzing, with harvesting by both hand and machine, crushing of the juice and the filling of giant fermentation tanks. Harvest fests are coming up.

Pretty soon, the fall foliage will make the trip even better.

What you'll sample in the winery tasting rooms is the product of previous years' harvests, but everyone always wants to know: What does this year's harvest look like?

"This year in the Finger Lakes looks like it's going to be a good year for the aromatic whites like gewurtztraminer, traminette and of course riesling," said Tim Martinson, senior vineyard specialist for Cornell University and its extension programs in Geneva. He was referring specifically to Upstate New York's pre-eminent wine region and its signature wine grapes.

The heavy rainfall and cooler temperatures in the spring and early- to mid-summer, combined with a mild winter last year, are making this an "ideal" season for those grapes, often referred to as "cool climate" varieties, Martinson said.

The berries on the vines are big and should be relatively free of disease and rot, he said. It's a contrast to last year, when a record drought brought an early and short harvest and low yields.

"This year is the complete opposite of that," Martinson said. The harvest should be able to stretch out well into October, he said. Overall, statewide, "this should be more of a 'normal year,'with grapes showing a good balance of sugar and acidity."

Different grapes ripen at different times, and so winemakers and Cornell experts are out now measuring sugars and watching other factors to determine when to start picking.

"We're a week behind on the harvest but the forecast right now is pretty good," said Jon Cupp, owner of Thirsty Owl Wine Co. in Ovid on Cayuga Lake. "It looks the berries are going to be able to mature for a while. It's going to be a good year for whites."

Of course, the winemakers and vineyard managers have become adept at dealing with whatever nature deals out.

"We always have weather," owner John Martini of Anthony Road Wine Co. on Seneca Lake likes to say. "The trick is figuring out how to make the best of the weather we've got."

Here's a sampling of some of the upcoming harvest festivals in the wine country. For a fuller list covering the Finger Lakes in particular, go to the Finger Lake Wine Country web site.

Harvest Festival (Niagara)

Celebrate the harvest at participating wineries along the Niagara Wine Trail, with food and wine pairings.


Pinot Noir in Harvest Bins

Because Pinot Noir is so old, it has had ample time to naturally mutate into new clones. This single grape variety has more than 1,000 registered clones! Pinot Noir is also the original member of the Pinot family, which spawned the natural mutations of the commonly found Pinot Meunier, Pinot Gris/Grigio and Pinot Blanc.

A message about clones: don’t panic! A clone does not mean a grape vine comes from genetically modified material or that it has morphed into something harmful. This is not a grape-based version of creating Dolly the Sheep.

The English word clone is based on a Greek word for twig and refers to the practice of generating a new plant, genetically identical to its parent, by taking and propagating a cutting. Unlike many agricultural crops, vines self-pollinate. Hence, they tend to be the same year after year after year. However, the older the domesticated variety, the greater is its tendency to morph. Pinot Noir clones have myriad characteristics. They can range from growing characteristics, such as early ripening or loose clusters, to aroma and texture features, like darker fruit flavors and super fine tannins.

The diverse range of Pinot Noir clones available adds to the complexity of the Pinot red wine variety. Moreover, sometimes the clones are vinified and bottled separately sometimes different clones are blended!

How to Plant, Grow, Prune, and Harvest Grapes

Dessert grapes and wine grapes are not difficult to grow in the home garden. Grapes grow well in most regions.

The most commonly grown grapes fall into two categories American grapes and European grapes. American grapes are most hardy they will grow in regions where winter temperatures fall to 0°F. European grapes are less hardy they can survive without damage where winter temperatures drop to 10°F. European grapes prefer a long, warm growing season—at least 170 frost-free days.

American and European hybrids (also called French-American hybrids) are resistant to fall and winter cold and require a long, warm growing season. They have the best qualities of both American and European varieties.

In warm, humid summer regions—such as the Southeast and South Central United States– Muscadine grapes are the best choice to grow. They thrive in the summer heat.

After selecting the right grape for your garden, growing and pruning grapes is not that difficult. For the most flavorful grapes and the best yield, you will want to spend a few hours in the first year or two training the vines and in subsequent years a few hours each season pruning the vines. The time investment for a good yield of flavorful grapes is minimal.

Grape Types

There are several types of grapes:

  • American, or fox, grapes (Vitis labrusca) are good growers they are for fresh eating or jelly. American grapes have soft flesh and musty flavor and aroma the pulp slides easily out of the skin.
  • European wine grapes also called Vinifera grapes ( vinifera) are used for making wine, fresh eating, and drying. They are less hardy than American grapes. European grapes have a mild flavor the fruit is firm and the skin does not slip off the flesh. European grapes are more susceptible to disease than other types.
  • French and American hybrid grapes have the best qualities of American and European grapes. They are vigorous growers they are resistant to winter cold and require a long, warm growing season. They have the strong flavor and aroma of American grapes and they have the firmer flesh and non-slip skin of European grapes.
  • Muscadine grapes ( rotundifolia) thrive in hot, dry regions they can be eaten fresh or made in jelly, juice, or wine. These grapes turn bronze, dark purple, or black when ripe.


Sacramento, CA

San Francisco

Fall is a beautiful time in Napa Valley, but it's also the busiest time of the year when workers of the wineries and the vineyards hurry to pick grapes at their peak ripeness. The peak season lasts from August through October, but some grape varieties can be harvested till late December. During this period, the whole valley is filled with unbelievable harvest fragrances, and the ideal warm autumn weather is here for you to enjoy.

Grapes used for sparkling wines are the first to be cautiously picked. The first harvest happens in early August and marks the start of the "crush" season. Then, a major part of the white grapes is harvested to be crushed. Harvest progresses through late October and early November—for red wines, just because it takes a bit longer for them to reach full maturity. Harvesting of Cabernet Sauvignon grapes in Napa Valley usually starts later and takes more time than other varieties. The production of late-harvest wines requires grapes to stay on the vines longer to allow them to get riper. Harvesting of these grapes can continue through December.

Here, in Napa Valley, you may also find numerous harvest dinners, parties, grape stomping, and other activities since harvest season is the peak season to visit Napa Valley.

The number of wineries around Napa is impressive, so why not get lost in William Hill Estate, Stags' Leap Winery, Odette Estate Winery, Chimney Rock Winery, Black Stallion Winery, and others?

How To Grow & Harvest Concord Grapes

Concord grapes are native to the United States and grow in most areas of the country. Concord grapes grow in large bunches suitable for juicing, jelly, wine making and eating. Plant bare-root Concord grape vines in the spring while the plants are dormant. Expect to harvest a few grapes the third year and a full crop during the fourth summer. Pick grapes when they are fully ripe, they do not sweeten after picking. Harvesting after a frost greatly increases the sweetness according to the Better Homes and Gardens “New Complete Guide to Gardening.”

Put the bare-root vines in a container of water with a small handful of bonemeal added. Allow the roots to soak for one to two hours before planting.

  • Concord grapes are native to the United States and grow in most areas of the country.
  • Plant bare-root Concord grape vines in the spring while the plants are dormant.

Remove grass and weeds from the planting site. Dig through the site to loosen the soil. Mix the top layer of soil with organic compost. Dig a hole large enough to accommodate the roots. Fan the roots out in the hole and cover them with soil.

Prune the vine after planting, leaving only one main stem with two buds.

Water regularly the first summer to keep the soil damp but not wet. Drip irrigation or a soaker hose is ideal. Decrease watering in the fall, watering only when the vine shows signs of wilting.

  • Remove grass and weeds from the planting site.
  • Fan the roots out in the hole and cover them with soil.

Remove all but one or two strong shoots during the first winter. These shoots will become the main trunk. Prune the remaining shoots back to two live buds.

Fertilize in the spring with two oz. of 10-10-10 fertilizer. Add an additional two oz. of fertilizer each year to a maximum of 16 oz. per vine.

  • Remove all but one or two strong shoots during the first winter.
  • Prune the remaining shoots back to two live buds.

Tie the shoots to a stake when they are six to 12 inches tall. Continue to loosely tie the shoots every 12 inches with cotton twine.

Prune the vine during the second winter, selecting two or three shoots to train into branches. Remove all other growth.

Train the shoots onto a fence or trellis during the following summer, removing all shoots until the lateral branches are the desired length. Once the branches have developed, allow shoots to grow.

Hand pick ripe grapes by pinching the cluster off at the vine. Grapes are ripe when the color deepens and the grapes taste sweet and juicy.

Watch the video: Ripening grapes in Eastern Canada: How climate affects grape potential for winemaking

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