The annual growth cycle of grapevines is the process that takes place in the vineyard each year, beginning with bud-burst in the spring and culminating with leaf fall in autumn followed by winter dormancy. From a winemaking perspective, each stage in the process plays a vital role in the development of grapes with ideal characteristics for making quality wine.

Viticulturists and winemakers monitor the effect of climate, vine disease and pests in assisting or impeding the vines progression from; bud-burst, flowering, fruit set, veraison through to harvest. Depending on specific vineyard temperatures, 40-80 days after bud-burst the process of flowering begins with small flower clusters appearing on the tips of the young shoots.

 

Flowering occurs when average daily temperatures stay between 15-20°C - which for Northern Hemisphere wine regions is generally around the month of May and for Southern Hemisphere wine regions this is around the month of November.
A few weeks after the initial clusters appear, the flowers start to grow in size with individual flowers become visible. It is during this stage of flowering that the pollination and fertilization of the grapevine takes place within about ten days - with the result being a grape berry, containing around 1-4 seeds.
Most Vitis Vinifera grape vines are hermaphroditic, meaning they have both male stamens and female ovaries, being able to self-pollinate. 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 (e.g. very cold temperatures, frosts, strong winds & heavy rain fall) can severely affect the flowering process, causing many flowers not to be fertilized.
Insects generally play only a minor role in aiding pollination, with the process being mostly self-contained within the grape vine. But cross-pollination between vine species is possible as in the case of the origin of the grape varietal like Cabernet Sauvignon - which is a natural cross pollination of Cabernet Franc and Sauvignon Blanc.