Pruning

Pruning of a young vine and an old wine.

In previous chapters we said that vines are delicate plants. Without attention, they degenerate, taking on a wild look and their production declines.

Pruning is an annual cutting operation; the wood is cut back to avoid the formation of dense foliage, to regulate production, to give consistency to the vine and to facilitate work on the soil.

Distinction can be made between "green" and "dry" pruning. The former is carried out in November or December, also in March, and the latter is done in January or February.

Generally, pruning time in the Rioja is in the middle of the winter, i.e., this involves "dry" or winter pruning. In the higher part of the Rioja Alavesa and Rioja Alta, which are prone to spring frosts, causing a disastrous effect on the quality of the wine, "green" pruning is carried out. After the grape harvest, the leaves wither and fall. The sap of the leaves and canes descends slowly towards the trunk to accumulate and form the winter reserves which will give strength to the new shoots. If we prune when the sap is descending, when the cane is still a little green, part of the sap is removed, i.e., the reserves which would accumulate in winter in the trunk are diminished and the spring shoots would have little strength. However the frosts might cause less damage as the sprouting of buds and leaves would be delayed.

If we prune in the middle of the winter, when the sap reserves have already descended to the trunk, it will bring about strong budding; the possible late frosts may damage tender parts of the vine. Therefore, "green" pruning, i.e., with sap in movement, delays budding and protects the vine against Spring or late Winter frosts, but "dry" pruning, in mid-winter does not defend the plant against this risk. But if pruning is left until late in March, when the vine has bled, generally the vineyard appears overgrown and makes this job difficult. In these cases "pre-pruning", or limited pruning is done, consisting of trimming the canes in December, and carrying out full pruning in March.

Rioja vines have a "goblet" shape, i.e., three ascending stems or "arms". Two "spurs" are left on each branch and two buds on each spur. In this way, the total number of buds per vine is twelve. If we consider that afterwards one cane sprouts from each bud and that each cane bears two clusters of grapes, we can deduce that each vine produces twenty-four bunches. But these theoretical equations are optimistic as there are numerous factors which reduce this amount, such as:

Sometimes deficiencies prevent the formation of three branches per vine. Spring frosts sometimes damage the buds.Flowering and fertilisation are not always the same, therefore the "cuajado", or "setting" of the cluster, is different each year, with more or less grapes. Blights and diseases can reduce or obliterate the growth of the clusters. The ripening conditions can increase or decrease the sugar inside the grape, producing clusters with different densities, therefore varying the weight attained the grape-harvest.

In this way we can understand that from twenty-four theoretical bunches, a much lower average, of variable weight, can be gathered per vine.

This type of pruning of twelve buds is typical in the Rioja but in some cases we can observe unorthodox methods which try to leave more than twelve buds to produce more bunches. This is what is called "long pruning". It is somewhat fraudulent and is forbidden by the Control of Origin Regulating Council of the Rioja. In the regulations they specify the pruning of twelve buds, and limit the final weight of grapes produced per hectare to 6,500 Kg of red grapes and 9,000 Kg of white grapes.

Is quantity the opposite of quality? Yes. When the vinegrower decides to obtain more grapes with "long pruning", the wine made is of inferior quality to that attained with authorised pruning methods.

Nevertheless, nature may replace these unauthorised methods; some years the weather conditions are so favourable that the amount of grapes obtained per hectare are extremely high and the quality of the wine is excellent. This was the case in 1964, 1970, 1981, 1985 and 1989.

"Two-bud" pruning on goblet-shaped vines is carried out by cutting the previous cane slightly above the two lower buds. Each year these buds are usually left on the lower cane. In this way the vine ascends in a gentle "V-shaped" zig-zag, but in the case of young vines the tendency is to leave the buds on the higher cane. In the case of very old vines, on the lowest canes, which are usually canes from the previous lower bud.

It has been seen that in western areas of the Rioja, grapes receive sufficient nutrients from the soil and products made in the leaves during vegetation; but bunches do not always receive optimum levels of illumination, being in the shade of twigs and leaves. Such lack of light might bring about low colour levels in cold years. To permit bunches to receive more light, pruning is sometimes made along wires, whereby twigs change from a vertical to a horizontal position. They are fastened in this position and exposed to light from the sides and above. In this case plantations are also made taking into consideration the width and orientation of the passageways, to gain maximum benefit from sunlight. On flat land, the advisable orientation for rows of vines is North-Northwest to South-Southeast.

Within prescribed production limits, this system of training vines can improve the quality of the grapes.

This system is also called "Quarante" pruning.