The Cycle Of A Wine Grape

Thursday, May 2nd, 2019
how wine is made

With Spring in full swing, it seems like a great time to learn about the growth of the wine grape. Grapevines go through an annual growth-cycle. The process begins 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.


Springtime in the vineyard brings bud break of the grapevines. This process generally begins in March. During the winter, the vines are pruned, which begins the process of the “bleeding” of the vine. The bleeding begins when the soil begins to warm and osmotic forces push water, containing a low concentration of organic acids, hormones, minerals, and sugars up from the root system and it is expelled from the cuts (or wounds) left over from pruning the vines. During this period, a single vine can “bleed” up to a gallon of water.

Tiny buds on the vine start to swell and eventually shoots begin to grow from the buds. Eventually, the shoots sprout tiny leaves that can begin the process of photosynthesis, producing the energy to accelerate growth.

Pollination and Flowering

Depending on temperatures, 40–80 days after bud break the process of flowering begins with small flower clusters appearing on the tips of the young shoots looking like buttons. Flowering occurs when average daily temperatures stay between 59–68 °F which is generally around May. A few weeks after the initial clusters appear, the flowers start to grow in size with individual flowers becoming observable. 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.

Most cultivated grape vines are hermaphroditic, with both male stamens and female ovaries.
Wind and insects generally only play a small role in aiding pollination, with the process being mostly self-contained within the vine. Cross-pollinations 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 (a French red grape). 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.

Fruit Set

The fruit set stage follows flowering almost immediately when the fertilized flower begins to develop a seed and grape berry to protect the seed. 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. Climate and the health of the vine play an important role – low humidity, high temperatures, and water stress have the potential of severely reducing the amount of flowers that get fertilized. 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.


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, usually in July. 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 lower.

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. It is considered ideal to have an early veraison for the production of high-quality wine. During this period, the cane of the vine starts to ripen, as well as changing from green and springing to brown and hard. The vines begin to divert some of their energy production into its reserves in preparation for its next growth cycle.


To a viticulturalist – the person in the business of growing grapes, the ultimate 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 New Mexico desert, this usually happens in August or September. 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.

The Cycle Continues

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 has been stored. At that point, the chlorophyll in the leaves begin 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.

The grape goes through a lot of development before it hits the bottle. Each season plays its important roll. You are always welcome to check out the vineyard at Heart of the Desert in Alamogordo to see the cycles. If all you really care about is the stuff that comes out of the bottle, stop in for some wine tasting and take home a bottle or three. Wine is also available for shipping to select states. See if you are one of the lucky ones by clicking here.

Heart of the Desert is a working pistachio ranch and vineyard with four retail establishments in New Mexico. They are best known for their farm fresh pistachios and Award-Winning New Mexico wines. Each store offers wine and pistachio tastings. They offer worldwide shipping and produce attractive gourmet baskets that make great corporate and family gifts. The main store, on the ranch in Alamogordo, offers farm tours that showcases how pistachios are grown and processed as well as a stunning Tuscany themed patio that overlooks the groves and is available for weddings, private parties or enjoying a relaxing glass of wine.