Annual growth cycle of grapevines

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Grape vine and fruit Grapes02.jpg
Grape vine and fruit

The annual growth cycle of grapevines is the process that takes place in the vineyard each year, beginning with bud break in the spring and culminating in leaf fall in autumn followed by winter dormancy. From a winemaking perspective, each step in the process plays a vital role in the development of grapes with ideal characteristics for making wine. Viticulturalists and vineyard managers monitor the effect of climate, vine disease and pests in facilitating or impeding the vine's progression from bud break, flowering, fruit set, veraison, harvesting, leaf fall and dormancy-reacting if need be with the use of viticultural practices like canopy management, irrigation, vine training and the use of agrochemicals. The stages of the annual growth cycle usually become observable within the first year of a vine's life. The amount of time spent at each stage of the growth cycle depends on a number of factors-most notably the type of climate (warm or cool) and the characteristics of the grape variety. [1]

Contents

Bud break

The bud of a Regent vine located between the stem and petiole. Regent Grape Vine with bud.jpg
The bud of a Regent vine located between the stem and petiole.

The grape starts its annual growth cycle in the spring with bud break. In the Northern Hemisphere, this stage begins around March while in the Southern Hemisphere it begins around September when daily temperatures begin to surpass 10 °C (50 °F). If the vine had been pruned during the winter, the start of this cycle is signaled by a "bleeding" of the vine. This bleeding occurs when the soil begins to warm and osmotic forces pushes water, containing a low concentration of organic acids, hormones, minerals and sugars, up from the root system of the vine and it is expelled from the cuts (or "wounds") left over from pruning the vine. During this period a single vine can "bleed" up to 5 litres (1.3 US gal) of water. [2]

Tiny buds on the vine start to swell and eventually shoots begin to grow from the buds. Buds are the small part of the vine that rest between the vine's stem and the petiole (leaf stem). Inside the buds contain usually three primordial shoots. These buds appear in the summer of previous growth cycle green and covered in scales. During winter dormancy they turn brown until the spring when the vine begins the process of bud break and the first sign of green in the vineyard emerges in the form of tiny shoots. [3] The energy to facilitate this growth comes from reserves of carbohydrate stored in roots and wood of the vine from the last growth cycle. Eventually the shoots sprout tiny leaves that can begin the process of photosynthesis, producing the energy to accelerate growth. In warm climates, after about 4 weeks the growth of the shoots starts to rapidly accelerate with the shoots growing in length an average of 3 cm (1 in) a day. [1]

In temperate climates, where temperatures can reach above 10 °C (50 °F) in mid-winter, some early budding varieties (such as Chardonnay) can be at risk of premature bud break. This is a potential viticultural hazard in places like the Margaret River region of Western Australia where warm currents from the Indian Ocean can coax Chardonnay vines to prematurely bud in the mid-winter month of July. After bud break, the young shoots are very vulnerable to frost damage with vineyard managers going to great lengths protect the fragile shoots should temperature dramatically drop below freezing. This can include setting up heaters or wind circulators in the vineyard to keep cold air from settling on the vines. [3]

Flowering

Developing inflorescences Vigne inflorescence 2.jpg
Developing inflorescences

Depending on temperatures, 40–80 days after bud break the process of flowering begins with small flower clusters resembling buttons appearing on the tips of the young shoots. Flowering occurs when average daily temperatures stay between 15–20 °C (59–68 °F) which in the Northern Hemisphere wine regions is generally around May and for the Southern Hemisphere regions around November. A few weeks after the initial clusters appear, the flowers start to grow in size with individual flowers becoming observable. [1] It is during this stage of flowering that the pollination and fertilization of the grapevine takes place with the resulting product being a grape berry, containing 1–4 seeds. [4]

The calyptra is shed and pollen is transferred from the anthers to the stigma fertilizing the flower. Vitis vinifera fleur 1.jpg
The calyptra is shed and pollen is transferred from the anthers to the stigma fertilizing the flower.

Most cultivated Vitis vinifera grape vines are hermaphroditic, with both male stamens and female ovaries, while many wild grapes are either male, producing pollen but no fruit, or female, producing fruit only if a pollinator is nearby. [5] Hermaphroditic vines are preferred for cultivation because each vine is more likely to self-pollinate and produce fruit.

At the beginning of the flowering process the only part that is visible is the fused cap of petals known as the calyptra. Shortly after the calyptra is shed, liberating the pollen from the anthers of the stamen. Wind and insects generally play only a small role in aiding pollination, with the process being mostly self-contained within the vine. But cross-pollination between vines of different varieties is possible: Cabernet Sauvignon is a cross of Cabernet Franc and Sauvignon blanc; Petite Sirah is a cross of Syrah and Peloursin. During the process of fertilization, the pollen fertilizes the ovary which produces seeds as the flower begins the transformation into a grape berry, encapsulating the seed. Detrimental weather (cold, wind & rain) can severely affect the flowering process, causing many flowers not to be fertilized and produce a group. [4] It is during this time when the buds that will become next years crops begin to form. [1]

Fruit set

Following fertilization, the fruit begins to form. Young grapes.jpg
Following fertilization, the fruit begins to form.

The stage of fruit set follows flowering almost immediately, when the fertilized flower begins to develop a seed and grape berry to protect the seed. In the Northern Hemisphere, this normally takes place in May and in the Southern Hemisphere in November. [1] This stage is very critical for wine production since it determines the potential crop yield. Not every flower on the vine gets fertilized, with the unfertilized flowers eventually falling off the vine. The percentage of fertilized flowers averages around 30 but can get as high as 60 or be much lower. Climate and the health of the vine play an important role with low humidity, high temperatures and water stress having the potential of severely reducing the amount flowers that get fertilized. Coulure occurs when there is an imbalance of carbohydrate levels in the vine tissues and some berries fail to set or simply fall off the bunch. Varieties like Grenache and Malbec are prone to this abnormal fruit set. Millerandage occurs when some fertilized flowers do not form seeds but only small berry clusters. Grape berry size depends on the number of seeds so berries with no seeds will be significantly smaller than berries containing seeds. On one cluster there may be berries of various sizes which can create problems during winemaking due to the varying "skin to pulp" ratio among the grapes. [6] This can be caused by vine disease, such as fanleaf, or by a boron deficiency in the vine. Gewürztraminer and the Chardonnay clones IA and Mendoza are both prone to millerandage. [7]

Veraison

A cluster of grapes undergoing veraison. Veraison.JPG
A cluster of grapes undergoing véraison.

Following fruit set, the grape berries are green and hard to the touch. They have very little sugar and are high in organic acids. They begin to grow to about half their final size when they enter the stage of veraison. This stage signals the beginning of the ripening process and normally takes place around 40–50 days after fruit set. In the Northern Hemisphere this will be around the end of July and into August and between the end of January into February for the Southern Hemisphere. [1] During this stage the colors of the grape take form—red/black or yellow/green depending on the grape varieties. This color changing is due to the chlorophyll in the berry skin being replaced by anthocyanins (red wine grapes) and carotenoids (white wine grapes). In a process known as engustment, the berries start to soften as they build up sugars. Within six days of the start of veraison, the berries begin to grow dramatically as they accumulate glucose and fructose and acids begin to fall. [8]

The onset of veraison does not occur uniformly among all berries. Typically the berries and clusters that are most exposed to warmth, on the outer extents of the canopy, undergo veraison first with the berries and clusters closer to the trunk and under the canopy shade undergoing it last. There are some factors in the vineyards that can control the onset of veraison, limited water stress and canopy management that creates a high "fruit to leaf" ratio can encourage veraison. This is because the vine is biologically programmed to channel all its energies and resources into the berries, which houses its seedling offspring, to provide them a better chance of survival. Conversely, very vigorous vines with plentiful leaf shading for photosynthesis and water supply will delay the start of veraison due to the vines energies being directed towards continued shoot growth of new buds. For the production of high-quality wine, it is considered ideal to have an earlier veraison. During this period the cane of the vine starts to ripen as well changing from green and springing to brown and hard. The vines begins to divert some of its energy production into its reserves in preparation for its next growth cycle. [8]

After harvest

Harvesting grapes Grape gathering.jpg
Harvesting grapes

In the vineyard, the antepenultimate event is the harvest in which the grapes are removed from the vine and transported to the winery to begin the wine making process. In the Northern Hemisphere this is generally between September and October while in the Southern Hemisphere it is generally between February and April. The time of harvest depends on a variety of factors-most notably the subjective determination of ripeness. As the grape ripens on the vines, sugars and pH increase as acids (such as malic acid) decrease. Tannins and other phenolics also develop which can affect the flavors and aromas in the resulting wine. The threat of detrimental weather and vine diseases (such as grey rot) can also play a role in the time table. The balance of all these factors contributes to when a winemaker or vineyard manager decides that it is time to harvest. [1]

Following the harvest, the vines continue the process of photosynthesis, creating carbohydrate reserves to store in the vine's roots and trunks. It will continue doing this until an appropriate level of reserves have been stored. At that point the chlorophyll in the leaves begins to break down and the leaves change color from green to yellow. Following the first frost the leaves begin to fall as the vine starts to enter its winter dormancy period. The following spring, the cycle begins again. [1]

See also

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Viticulture Cultivation and harvesting of grapes

Viticulture or winegrowing is the cultivation and harvesting of grapes. It is a branch of the science of horticulture. While the native territory of Vitis vinifera, the common grape vine, ranges from Western Europe to the Persian shores of the Caspian Sea, the vine has demonstrated high levels of adaptability to new environments, hence viticulture can be found on every continent except Antarctica.

Durif Red wine grape

Durif is a variety of red wine grape primarily grown in Australia, California, France, and Israel. Since the end of the 20th century, wineries located in Washington's Yakima River Valley, Maryland, Arizona, Texas, West Virginia, Chile, Mexico's Baja California Peninsula, and Ontario's Niagara Peninsula have also produced wines from Durif grapes. It is the main grape known in the U.S. and Israel as Petite Sirah, with over 90% of the California plantings labeled "Petite Sirah" being Durif grapes; the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) recognizes "Durif" and "Petite Sirah" as synonyms for the same grape. It produces tannic wines with a spicy, plummy flavour. The grape originated as a cross of Syrah pollen germinating a Peloursin plant. On some occasions, Peloursin and Syrah vines may be called Petite Sirah, usually because the varieties are extremely difficult to distinguish in old age.

Condrieu AOC

Condrieu is a French wine-growing Appellation d'Origine Contrôlée (AOC) located in the northern Rhône, near Vienne and to the south of the Côte-Rôtie AOC. The vineyards are situated in the seven communes of Limony, Chavanay, Malleval, Saint-Michel-sur-Rhône, Saint-Pierre-de Boeuf, Vérin, and Condrieu. These communes are in the French departments of Ardèche, Rhône and Loire on the steep slopes of the foothills of the Massif Central on the right bank of the Rhône. The four southernmost communes can also produce wine under the Saint-Joseph AOC. The wines made in this AOC are exclusively white, from the Viognier grape, which may have originated in the region. The smaller AOC of Château-Grillet is enclaved within Condrieu and produces wines that are also 100% Viognier. The Condrieu AOC was officially created in 1940.

Agiorgitiko Variety of grape

Agiorgitiko is a red Greek wine grape variety that, as of 2012, was the most widely planted red grape variety in Greece, ahead of Xynomavro. The grape has traditionally been grown in the Nemea region of the Peloponnese but can be found throughout the country including Attikí (Attica) and Makedonía (Macedonia).

Millerandage

Millerandage is a potential viticultural hazard problem in which grape bunches contain berries that differ greatly in size and, most importantly, maturity. Its most common cause is cold, rainy or otherwise bad weather during the flowering stage of the vines though other factors, such as boron deficiency or fanleaf degeneration, may also play a role.

Coulure

Coulure is a viticultural hazard that is the result of metabolic reactions to weather conditions that causes a failure of grapes to develop after flowering. In English the word shatter is sometimes used. Coulure is triggered by periods of cold, cloudy, rainy weather or very high out-of-season temperatures. The condition is most often manifested in the spring. It also occurs in vines that have little sugar content in their tissue. Flowers stay closed and are not fertilized. Thus the vines are not pollinated as the grape fails to develop and falls off. Coulure can also cause irregular bunches of grapes which are less compact than normal. These bunches are more sensitive to developing various grape diseases. The yield of a vine with coulure will decrease substantially. Grape varieties with high proclivity to coulure are Grenache, Malbec, Merlot, and Muscat Ottonel. Other causes of coulure may be vineyard conditions and practices, pruning too early or too severely, excessively fertile soils or overuse of fertilizers, and improper selection of rootstocks or clones.

<i>Vitis</i> Genus flowering plants in the grape family Vitaceae

Vitis (grapevines) is a genus of 79 accepted species of vining plants in the flowering plant family Vitaceae. The genus is made up of species predominantly from the Northern Hemisphere. It is economically important as the source of grapes, both for direct consumption of the fruit and for fermentation to produce wine. The study and cultivation of grapevines is called viticulture.

Harvest (wine) Harvest of grapes in order to produce wine

The harvesting of wine grapes (Vintage) is one of the most crucial steps in the process of wine-making. The time of harvest is determined primarily by the ripeness of the grape as measured by sugar, acid and tannin levels with winemakers basing their decision to pick based on the style of wine they wish to produce. The weather can also shape the timetable of harvesting with the threat of heat, rain, hail, and frost which can damage the grapes and bring about various vine diseases. In addition to determining the time of the harvest, winemakers and vineyard owners must also determine whether to use hand pickers or mechanical harvesters. The harvest season typically falls between August & October in the Northern Hemisphere and February & April in the Southern Hemisphere. With various climate conditions, grape varieties, and wine styles the harvesting of grapes could happen in every month of the calendar year somewhere in the world. In the New World it is often referred to as the crush.

Klevener de Heiligenstein

Klevener de Heiligenstein, also known in English by its German name, Heiligensteiner Klevener, is a designation used on Alsace wine made from pink-skinned Savagnin rose grapes, a variety in the Traminer family, but which is less aromatic than Gewürztraminer, which is widely planted in Alsace. The designation may be allowed for selected vineyards in the villages Bourgheim, Gertwiller, Goxwiller, Heiligenstein and Obernai but, under current appellation rules, the designation may be used until 2021 for specified existing vineyards outside the designation area. Since Savagnin rose is not a permitted variety for other Alsace wines, its replanting outside this area is not allowed.

Canopy (grape) Grapevine structure above ground

In viticulture, the canopy of a grapevine includes the parts of the vine visible aboveground - the trunk, cordon, stems, leaves, flowers, and fruit. The canopy plays a key role in light energy capture via photosynthesis, water use as regulated by transpiration, and microclimate of ripening grapes. Canopy management is an important aspect of viticulture due to its effect on grape yields, quality, vigor, and the prevention of grape diseases. Various viticulture problems, such as uneven grape ripening, sunburn, and frost damage, can be addressed by skillful canopy management. In addition to pruning and leaf trim, the canopy is often trained on trellis systems to guide its growth and assist in access for ongoing management and harvest.

Acids in wine

The acids in wine are an important component in both winemaking and the finished product of wine. They are present in both grapes and wine, having direct influences on the color, balance and taste of the wine as well as the growth and vitality of yeast during fermentation and protecting the wine from bacteria. The measure of the amount of acidity in wine is known as the “titratable acidity” or “total acidity”, which refers to the test that yields the total of all acids present, while strength of acidity is measured according to pH, with most wines having a pH between 2.9 and 3.9. Generally, the lower the pH, the higher the acidity in the wine. There is no direct connection between total acidity and pH. In wine tasting, the term “acidity” refers to the fresh, tart and sour attributes of the wine which are evaluated in relation to how well the acidity balances out the sweetness and bitter components of the wine such as tannins. Three primary acids are found in wine grapes: tartaric, malic, and citric acids. During the course of winemaking and in the finished wines, acetic, butyric, lactic, and succinic acids can play significant roles. Most of the acids involved with wine are fixed acids with the notable exception of acetic acid, mostly found in vinegar, which is volatile and can contribute to the wine fault known as volatile acidity. Sometimes, additional acids, such as ascorbic, sorbic and sulfurous acids, are used in winemaking.

Phenolic content in wine Wine chemistry

The phenolic content in wine refers to the phenolic compounds—natural phenol and polyphenols—in wine, which include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids, stilbenoids, flavonols, dihydroflavonols, anthocyanins, flavanol monomers (catechins) and flavanol polymers (proanthocyanidins). This large group of natural phenols can be broadly separated into two categories, flavonoids and non-flavonoids. Flavonoids include the anthocyanins and tannins which contribute to the color and mouthfeel of the wine. The non-flavonoids include the stilbenoids such as resveratrol and phenolic acids such as benzoic, caffeic and cinnamic acids.

This glossary of viticultural terms list some of terms and definitions involved in growing grapes for use in winemaking.

Ripeness in viticulture

In viticulture, ripeness is the completion of the ripening process of wine grapes on the vine which signals the beginning of harvest. What exactly constitutes ripeness will vary depending on what style of wine is being produced and what the winemaker and viticulturist personally believe constitutes ripeness. Once the grapes are harvested, the physical and chemical components of the grape which will influence a wine's quality are essentially set so determining the optimal moment of ripeness for harvest may be considered the most crucial decision in winemaking.

Irrigation in viticulture Process of applying extra water in the cultivation of grapevines

Irrigation in viticulture is the process of applying extra water in the cultivation of grapevines. It is considered both controversial and essential to wine production. In the physiology of the grapevine, the amount of available water affects photosynthesis and hence growth, as well as the development of grape berries. While climate and humidity play important roles, a typical grape vine needs 25-35 inches of water a year, occurring during the spring and summer months of the growing season, to avoid stress. A vine that does not receive the necessary amount of water will have its growth altered in a number of ways; some effects of water stress are considered desirable by wine grape growers.

Vine training

The use of vine training systems in viticulture is aimed primarily to assist in canopy management with finding the balance in enough foliage to facilitate photosynthesis without excessive shading that could impede grape ripening or promote grape diseases. Additional benefits of utilizing particular training systems could be to control potential yields and to facilitate mechanization of certain vineyard tasks such as pruning, irrigation, applying pesticide or fertilizing sprays as well as harvesting the grapes.

Pixie Grape Variety of grape

The Pixie Grape is a new type of Vitis vinifera cultivar. The Pixie is a natural dwarf grapevine that is derived from the periclinal L1/L2 chimera Pinot Meunier. These dwarf grapevines tend to have short internodes and prefer to grow flowers instead of tendrils. They grow from 1 foot to 2 feet in height and produce clusters with a size on average of 4 inches. It is simple to cultivate in greenhouses and grows year round. Its purpose was to create an easy tool with which to conduct grapevine research. The grape was developed by grape rootstock breeder Dr. Peter Cousins of the USDA.

Cabernet blanc is a white German and Swiss wine grape variety that is a crossing of the French wine grape Cabernet Sauvignon and Regent. The grape was bred by Swiss grape breeder Valentin Blattner in 1991. Cabernet blanc has strong resistance to most grape disease including botrytis bunch rot, downy and powdery mildew and tends to produce loose clusters of small, thick-skinned grape berries which can hang on the vine late into the harvest season to produce dessert wines. Today the grape is found primarily in the Palatinate wine region of Germany with some experimental plantings in Spain and the Netherlands. In France, in the Languedoc, Domaine La Colombette is heavily investing in PIWI grapes. Amongst others the Cabernet Blanc in their cuvée "Au Creux du Nid", is gaining wide acclaim.

Propagation of grapevines

The propagation of grapevines is an important consideration in commercial viticulture and winemaking. Grapevines, most of which belong to the Vitis vinifera family, produce one crop of fruit each growing season with a limited life span for individual vines. While some centenarian old vine examples of grape varieties exist, most grapevines are between the ages of 10 and 30 years. As vineyard owners seek to replant their vines, a number of techniques are available which may include planting a new cutting that has been selected by either clonal or mass (massal) selection. Vines can also be propagated by grafting a new plant vine upon existing rootstock or by layering one of the canes of an existing vine into the ground next to the vine and severing the connection when the new vine develops its own root system.

References

  1. 1 2 3 4 5 6 7 8 J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 741–742 Oxford University Press 2006 ISBN   0-19-860990-6
  2. ↑ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 82 Oxford University Press 2006 ISBN   0-19-860990-6
  3. 1 2 J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 107 Oxford University Press 2006 ISBN   0-19-860990-6
  4. 1 2 J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 276 Oxford University Press 2006 ISBN   0-19-860990-6
  5. ↑ Reisch, Bruce; Stewart, Philip (2001). "Grape Breeding Procedures". Cornell Grape Breeding. Retrieved 16 November 2015.
  6. ↑ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 291 Oxford University Press 2006 ISBN   0-19-860990-6
  7. ↑ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 443 Oxford University Press 2006 ISBN   0-19-860990-6
  8. 1 2 J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 730 Oxford University Press 2006 ISBN   0-19-860990-6
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