701.9 Grapevines, Grape Physiology & Ampelography

Learn the terms and understand how the grape develops and any vigneron or winemaker will be impressed by your knowledge. They might even open up a rare bottle that they wouldn’t have otherwise do for other visitors.

GRAPE PHYSIOLOGY

The grape has four essential parts: Stalk, Skin, Pulp & Seed

Figures 1 and 2 show the names of the various parts of the grapevine and the grape bunch. Each bunch has a stalk that is discarded at the beginning of the wine making process The stalk makes up 3 % to 5 % of the total weight.

Figure 3 shows the useful parts of the grape berry for the production of wine.

The skin (6 % to 10 % of total weight) or peels of grapes contain anthocyanins or coloring substances and tannins as well as yeast that enable the juice to ferment.

The pulp (82 % to 90 % of total weight) is source of grape juice and consists of water, sugars, acids, mineral substances and vitamins.

The seeds (2 % to 4 % of total weight) are rich in tannins and oils.

Figure 4 & 5, shows you the first year’s development of rachis that leads to the production of fruit only in the second year.

a. Flower Development and Budbreak leading to the first foliage


In early spring, the vine awakens from its dormancy over winter. Sap rises to the pruned shoots and as the ambient temperature rises, the bud swells up, bursts and the first foliage or shoots and leaves emerge.

b. & c. Bloom or Flowering to Fruit Set

Flowering lasts about 10 days in early summer and then the flowers themselves develop into miniature grapes. Unfertilized flowers drop off. Veraison is a term used to indicate when the grapes change colour from small green shot/pellets and double in size.

d. Ripening and Harvest

Some varieties ripen faster than others. Once there is sufficient sugar in the grape, and acidity levels well balanced, the grape is ready for harvest. Flavour, tannins and colour are also considerations. After harvest, the leaves turn colour and fall off and the vine enters a period of Endodormancy.

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