The Life Cycle of a Grape
One Year in the Vineyard
Winter Dormancy
December-March (Jun-Sep)
Sleeping vines at the Moselle (Mosel, Germany) in February.
Dormancy is a stage with no growth activity. The vine rests from autumn (leaf fall) to spring (bud burst).
The drop in temperatures triggers the dormancy. The vine stores its nutrients (carbohydrates) in the cordon, trunk, and roots, and the vine loses water (dehydrates) to avoid winter frost damages.
At this stage, the leaves fall off, and the soft shoots get woody and turns into next year new canes.
Winter Dormacy Risks
In continental climates, winter frost can damage the new buds, or even kill the whole plant.
Winter Pruning
December-March (Jun-Sep)
Winter pruning is a selective removal of 70-90% of the branches and buds.
The first round of winter pruning removes the majority of the canes (70-90%) to allow a more precise bud selection at a later pruning.
Fruit is produced only on shoots from one year old branches, so the goal of the pruning is to maximize their amount. Pruning also assures maximum energy and nutrients to the fully ripen grapes.
Pruning Risks
Too much vegetation could result in lack of nutrients, excessive shading, high crop load, uneven ripening and encourage diseases.
It is necessary to prune every year. Pruning should occur late in the dormant season and before budbreak.
Bud Break (Budding - Budburst)
March-April (Sep-Oct)
Budding is the first sign of life.
Budding is the first sign of life. The vine is weaking up and needs to produce leaves to generate carbohydrates (via photosynthesis) to fuel the new growth.
Bud Break happens when daily temperatures reach 10 °C (50 °F). The vine enters a new growing season trained to a particular system and pruned to a certain number of buds.
As temperature and light increase, starches (stored carbyhydrates) are converted into sugar, and fluid begins to move in the vine. As the activity accelerates, branches can grow 5-15 cm each day, and buds swell and generate new shoots.
Bud Break Risks
In the bud break period, buds are delicate and vulnerable to frost and hailstorms. In 2016, in Beaujolais in France, some vineyards lost up to 100% of their buds from hail.
Spaying against diseases (if allowed) begins at bud break.
Flowering
April-May (Oct-Nov)
Flowering can last one or two days in a warm and dry climate, or one month in a cool and wet climate.
Grapevine flowers bloom in a cluster 6 to 9 weeks after bud break. Flowering depends on warmer temperature and stronger sunlight: a daily temperature of 15-20 °C (59–68 °F) activates the process.
Domesticated Vitis Vinifera varietals are hermaphroditic: the blossoms self-pollinate, without help from bees, because flowers are bisexual (have both sexes).
Pollen from a male flower (stamen) fertilizes the female flower (ovary), and a seed (embryo) develops. The entire ovary grows to become the grape berry itself with seeds contained within.
Flowering Risks
Flowers are delicate and vulnerable to harsh wind, cold and heavy rain.
Fruit Set
May-June (Nov-Dec)
Small green peppercorn-sized berries grow bigger and harder, high in acid and low in sugar.
Fruit set is the stage immediately after flowering.
As temperature rises, the growth accelerates, shoots expand and the vine starts to produce new nutrients via photosynthesis. There are hundreds of flowers in a grape inflorescence (the group of flowers on a stem). However, a relatively low percentage of these flowers will form a grape.
Fruit Set Risks
Wet, cloudy, and rainy weather reduces fruit set percent. Clear, warm weather improves fruit set percent.
Coulure: When more flowers fail to fertilise into grapes.
Millerandage: When grapes form without seed.
Cluster Thinning (Green Harvest)
From July to August, cluster thinning takes place to ensure optimal ripening.
Undersized an immature bunches are removed to save energy to the remaining (best quality) grapes.
Leaf Removing
Leaf removing assures higher quality wine.
It reduces the energy used on leaves, maximises the exposure to sunlight, provides good air circulation, and reduces the risk of diseases.
In cool climates it also helps the fruit to ripen by clearing the shade.
Ripening (Véraison)
July-September (Jan-Mar)
Grapes start green, then they turn yellow or pink, (white grapes) or red, blue, purple or black
Ripening happends in July/August (South: Jan/Feb).
It is the stage where the grapes begin to change color.
This is a signal of fruit maturation (ripening), berries begin to soften, acid level falls and sugar level rises.
The balance between sugars and acids is the most critical aspect to determine the quality of the wine. The longer the grape is on the vine, the higher the sugar and the lower the acidity will be.
Veraison is uneven (different degrees of ripeness) and the berries exposed to more sun and light get a head start.
Harvesting
September-October (March-April)
Hand picking Gruner Veltliner grapes at Hahndorf Hill vineyard in the Adelaide Hills
Several harvesting factors can significantly influence the quality of wine:
Harvest Timing
Harvesting Methods
Sorting Methods
Crushing Methods
The enologist chooses when to harvest, usually between September-October (South: March-April).
If you pick too early, the tannins are green and bitter. If you pick too late, the sugar level kills the acidity.
Generally, harvesting takes from one week to a month of hard labor. Once you start, you can't stop. The main factors are maturity (skin thickness, berry texture, seed and stem color), optimal PH, sugar and acidity levels, optimal ripeness, wine style, weather forecasts, etc.
Sparkling wines need high acidity, so the harvest is early.
Dessert wines need high sugar, so the harvest is late.
White grapes mature sooner and are normally harvested before black grapes that need more time to achieve the ideal color and sugar-acid balance.
Harvesting grapes at the optimal ripeness level is critical for preserving acidity, sugar content, and flavor development. Winemakers carefully monitor grape maturity through visual inspection, tasting, and chemical analysis to determine the ideal harvest timing.
Harvesting Risks
The disease enemy at the harvesting period is the fungal infection Botrytis that causes grapes to rot under rain-induced humidity.
Timing and the methods of grape harvesting are critical.
Hand-harvesting versus mechanical harvesting can also impact grape quality. Hand-picked grapes have better quality because grapes are delicate and break easily during machine harvesting. Broken grape skins can result in premature start of fermentation.
Harvesting too early or too late can result in underripe or overripe grapes, affecting the balance of flavors and acidity in the wine.
Sorting and Crushing
After harvesting, grapes are sorted to remove any damaged or underripe fruit. Crushing or destemming then breaks the grape skins to release juice and begins the process of extraction.
Human Factors
Human factors in a vineyard, including the decisions and practices of vineyard owners, managers, and winemakers, have a significant impact on the style, quality, and price of wine.
Human factors can complement or even override the natural influences of the terroir.
The combination of human decisions and practices together with natural factors defines the unique character of each wine and its market appeal.
Quality Control
Rigorous quality control during grape sorting, crushing, and winemaking ensure that only the best fruit is used and that the winemaking process is consistent.
Ensuring consistent quality is essential for maintaining a winery's reputation. Quality control measures include monitoring grape quality, hygiene standards in the winery, and tasting evaluations throughout the winemaking process. Consistent quality helps establish trust with consumers and may justify higher prices.
