Preparing for a Successful Harvest

By Dana Hinders

Most vineyards in North America and Europe will harvest grapes in August, September, and October. Typically, sparkling wine grapes are harvested first to ensure lower sugar levels, followed by the white wine grapes. Red wine grapes take a bit longer to reach full maturation, so they’re harvested later in the season. Finally, the grapes for ice wines make their way to crush, as it’s desirable they dehydrate on the vine to create a raisin-like grape with highly concentrated sugars.

  In most cases, a vineyard manager will check the grapes every day during the week or two before the scheduled harvest date because each part of the vineyard must be harvested at precisely the right moment. Matthew Clark, Assistant Professor of Grape Breeding and Enology at the University of Minnesota, says that understanding basic juice chemistry isn’t as difficult as it sounds. “The question is ‘Do I have enough sugar to make my wine product?’ Higher sugar grapes provide you with higher alcohol content in your wine. If there’s not enough sugar in your grapes, you can’t make wine without adding additional sugar. The best way to test sugar levels is with a handheld refractometer, either analog or digital. Each variety has a known point at which sugar levels won’t increase.”

  It’s usually preferable to harvest when temperatures are coolest. The cooler temperatures during the evening hours make grapes firmer and easier to de-stem, as well as creating better working conditions for those in the field. And, by harvesting at night, your grapes will already be closer to the temperature needed during the cold soaking process. “In order to reduce high fruit temperatures during harvest, which accelerates deterioration and demands more energy to cool fruit down further, harvest should be carried out early in the morning when temperatures are cooler or at night if a grower has sufficient lighting,” according to Elizabeth Wahle of the University of Illinois Extension Office. “Morning harvested grapes should be kept shaded until moved to a cooling unit.”

Choosing a Harvest Method

  Traditionally, all vineyards were harvested by hand. Hand harvesting gives you more control over the process and has the advantage of doing a better job of protecting the grape’s juice content from the oxidation caused by damaged skins. Mosbah Kushad, Postharvest Horticulturist at the University of Illinois, recommends hand harvesting if possible. “The biggest concern is fruit injury,” he said. “Damaged fruits enhance the rate of fungal and bacterial growth due to the seepage of their sugars. Damaged fruits also attract insects that could affect the quality of the finished product. For a small grower, hand harvesting is the way to go.”

  The main disadvantage of hand harvesting is the amount of labor required. If you can’t recruit temporary laborers or volunteers from the community, you may need to advertise on a site such as However, Clark stresses that your labor force has to be flexible. “The biggest mistake I see smaller growers making is picking when labor’s available,” he said. “If you arbitrarily schedule harvest for Saturday and the grapes aren’t ready until the following Wednesday, you won’t happy with the results. Garbage in, garbage out is a computer science mantra with relevance to winemaking. For quality wine, you need quality fruit.”

  When hand harvesting, you’ll need to make sure your buckets are cleaned and sanitized before the big day. Sharpen your picking slips and lubricate them with a bit of olive oil. Provide cotton picking gloves for all your workers to protect against small cuts as well as the risk of bee stings.

  Mechanical harvesting is efficient and cost-effective. “Labor availability and quality is a big factor in choosing mechanical harvesting,” says Eric T. Stafne, an Associate Extension/Research Professor at Mississippi State University. “Economics is another. There is a certain economy of scale that makes it worthwhile to have harvest equipment. The market for the fruit may also dictate which method is used.”

  The mechanical harvest method works best for large vineyards that lay on a flat patch of ground, where the rows have been laid out straight, and the posts are of uniform height.  Additionally, harvesters shouldn’t be operated near ditches, embankments, holes, steep slopes, or within 15 feet of electrical wires.  Even for vineyards prepared with mechanical harvesting in mind, it’s always a good idea to do a pre-harvest survey for low hanging limbs, wires, or any obstacle that could obstruct the path of the harvester.

Post-Harvest Essentials

  As a winemaker, you want to avoid “reinventing the wheel” with each vintage you produce. This is why it’s crucial that you keep accurate records throughout the harvest process. Don’t expect to rely on your memory to recall the exact brix and pH you want or your average crop load per vine. Jot down relevant details on a notebook in your pocket or use a voice recording app on your smartphone. When the harvest is over, transfer everything to a spreadsheet so you’re ready for the following year.

  “At a minimum, records should be maintained to monitor vine balance: dormant pruning weights and yields are used to calculate crop load (Ravaz index),” Wahle said. “Over the years, this helps determine the impact of management and fruit quality. Yield can be estimated by keeping track of the number of vines per block, the average number of clusters per vine, and average cluster weights annually at harvest.”

  You’ll also need to tend to your field after your grapes have been picked. “Don’t forget the vines after harvest,” Stafne said. “They may need fungicide and insecticide applications to retain leaves, irrigation during dry periods, etc. to reduce vine stress and promote good health going into fall and winter. This will reduce chance for winter injury and encourage bud fruitfulness in the following year.”

  Vines should be pruned in winter when they are fully dormant. Without the leaves in the way, it’s easier to see the structure of the plant. When pruning, promptly remove and dispose of any diseased wood with lesions or sap, grapes that didn’t ripen, mold, and discolored leaves. Sterilize your pruning equipment by dipping the cutting blades in a solution of isopropyl alcohol after you’ve finished with each vine.

Harvest Time at Adelaida

  Located just 14 miles from the Pacific Ocean, Adelaida’s family-owned vineyards are in the mountainous terrain of Paso Robles’ Adelaida District. “We are one of the oldest wineries in Paso Robles, established in 1981,” explained Glen Mitton, winery and vineyard ambassador. “Our estate vineyards are planted between 1,650 ft. and 1,980 ft. We own the oldest continually producing Pinot Noir Vineyard in the Central Coast, planted in 1964. Our soil is a diverse combination of limestone, chalk, and clay with amazing water retention properties to enable us to dry farm 30% of our vineyards and also 100% of our 700 plus acres of walnuts.”

  The vineyards are farmed with Earth-friendly practices, which earned Adelaida the honor of being named a Certified California Sustainable Winegrowing Winery & Vineyard (CCSW) in 2015. “We pick our grapes based on flavors and condition of plant, as our winemaker is in the vineyard daily,” remarked Mitton. “We hand harvest all of our 157 acres of estate vineyards at night usually starting at midnight. Grapes are placed and transported from vineyard to winery in 20 lb. trays. While each year is different, we find our estate vineyard is a four to six weeks harvest process.”

Harvest Time at Laurita Winery

  Central New Jersey’s Laurita Winery is committed to creating wines that derive as much character from the fruit as possible. They pride themselves on being responsible stewards of the land, with 43 fully cultivated acres of vineyards and 200 acres of woodlands, meadows, and pasture. “We hand pick based on what varieties are ripe at the time,” noted Nicolaas Opdam, Oenologist/Vineyard Manager. “The process is monitored carefully. We take samples for two to three weeks to monitor sugar levels and pH. Since each grape variety ripens at its own pace, we usually have a few days between harvest sessions. This makes us fortunate to have a little flexibility in scheduling our labor force.”

  Laurita Winery employs staff members, their families or friends, and seasonal labor to pick the grapes. The pickers are taught to pay close attention to the vines, only picking the highest quality grapes. A second sorting occurs after picking to make sure damaged grapes or foreign material is removed. Opdam commented, “We’re an old school winemaker.  We watch the weather forecast and the condition of the vines carefully, but there’s a family feel to the whole harvest process.”

Harvest Time at Garvin Heights Vineyards

  In Winona, Minnesota, Garvin Heights Vineyards specializes in the growing of cold climate grapes developed by the University of Minnesota and Elmer Swenson. Made by cross breeding native American varieties with those from Europe, their grapes can withstand Minnesota’s colder temperatures while producing wine similar to what you might find in more traditional growing areas.

  According to co-owner Linda Seppanen, deciding when to harvest involves several factors. “Our primary chemistry considerations are the brix (sugar level) plus the acid level for the style of wine that we are intending to make,” she shared. “Along with this is when we can get a picking crew, what the weather will be, if we are having a lot of bird pressure even through the netting, and when the Asian Lady Beetles numbers are getting bad.”

  To find supplemental labor for their hand picking, Garvin Heights Vineyards enlists the help of local students. They also work with clubs that want to earn money for extracurricular activities, thereby streamlining the harvest process while also helping to support the community.

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