Bud (vine)

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 vines 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.

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.

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