The vegetative cycle of the wine

The productive life of the vine lasts a good number of years, sometimes up to a hundred, but provides grapes for efficient winemaking for about fifty years. There is an annual vegetative cycle which culminates with the grape harvest and restarts the following year. This cycle, unlike many crops, coincides with the calendar year. The inactive period for the vine spans a period, the approximate midpoint of which is the end of one year and the beginning of the next. Accordingly, when we speak of a wine harvest, for example the famous vintage of 1964, we do not only refer to the grape harvest of 1964 but to the whole cycle of the vine which produced grapes in that year.

The annual cycle of the vine consists of different stages which we are going to explain in a simplified way with reference to the calender.

January. The vine rests from November and continues in its latent condition until March when, with the increase in temperature, it initiates its activity. During this period, pruning takes place. This must be done by the vinegrower to remove inefficient shoots from the previous year and give the vine the desired shape and productivity for the new cycle.

March. The "lloro" or bleeding is the first indication of activity in the vine each year. It lasts about three weeks and receives this name from a colourless liquid that flows from the pruning cuts. This liquid changes rarely, but when it does, it takes on a curious red appearance which vinegrowers call "lloro sangrante".

April. When a temperature of ten degrees is reached, bud break occurs; this begins with a thickening of the buds followed by the separation of the scales which have protected them. Some small initial leaves appear or "foliation".

May. At the end of this month, "flowering" takes place. This consists of the opening of the flower with the shedding of the corolla and fertilisation. Sometimes, due to a lack of heat, an excess of humidity or abnormal vigour, the flower does not become totally fertilized, giving bunches with a small number of grapes. It is said then that there has been "corrimiento de la flor", in other words, the flower has not been completely fertilized. Fertilization is popularly called "cuajado" or "setting". The very small initial fruit, which forms the bunch, is very bitter and green. The bunches are called "agraces" or unripe berries and this condition, which lasts until July, is called "agraz".

July. When the month of July arrives, the vine reaches its physiological maturity. It could now reproduce itself, but the fruit is still a long way from being a ripe grape, although the evolution which will end in the grape harvest has already begun. During this month, the stage called "envero" or veraison becomes apparent. The grapes change colour, from green to a yellowish colour in the white varieties and pinkish in the red varieties. Until then it is impossible to distinguish between a bunch of white grapes and a bunch of red grapes. In addition, the grape begins to lose acidity and accumulate sugar.

September. The newly coloured grapes change from being very bitter to very sweet. The skin of the grape softens steadily and the red varieties take on an intense colour. This is the ripening stage, the end of which is difficult to define but concludes with the harvest.

October. Harvesting takes place, and consists of cutting the bunches for wine-making. The enologist will judge when this is advisable, depending on the type of wine which is required. If it is brought forward, the wines are fresh and green; if it is put back, wines of higher alcohol content and more colour are obtained.

November. The vine begins to wither even before the harvest. It is a progression towards the latent winter stage. The vine leaves harden, the sap accumulates in the stem, the leaf changes to a tobacco colour and falls. In March another cycle will initiate with the "lloro" or bleeding.