Pruning calls for some thought. A shoot will grow 6m (20ft) in a single season, and every eye along the entire length is capable of bearing a shoot which will produce one or more bunches of grapes. In addition, a vine is able to bear fruit on the older wood, though this would prove too much for its constitution. If new shoots are encouraged, the eyes on the old wood will not be sufficiently vigorous to bear fruit, and the fruit on the new wood will be better.
There are two main methods of pruning, the long rod system and the spur system.

The long rod system – This name applies when one or two new shoots or rods are allowed to grow on and all other growth is restricted.
With vines, pruning is done in the depths of winter, the first days of January, before the sap begins to rise, being most suitable. For greenhouse plants, allow the vine to form two stems or rods; train these as far apart as possible and tie in to wires stretched across the roof. The rods will grow 6m (20ft) or more their first year. On New Year’s Day, cut the weaker rod back to two buds near the base. On the other, stronger stem will be borne the season’s crop, and the stronger stem from its two buds will be grown on to produce the crop for the season after that. To prevent the formation of too much foliage, pinch back all laterals to two buds – one to bear the fruit, the other the foliage, which should be stopped at two leaves. Do this pinching back of laterals in summer over several weeks so as not to check the plant too drastically.
During the first year, no vine should be allowed to fruit, and the following year only one bunch from each lateral should be retained.
Should it happen that buds on the lower part of the rods refuse to come into growth, lower the rod from the roof for three or four weeks before tying it in again. This will persuade the lower buds to ‘break’ whilst retarding the upper buds at the same time. For vines in the open, growing vertically, follow the single rod and spur system, retaining the strongest shoot of two basal buds to bear fruit. Then, after fruiting, cut back to a single eye or bud to produce next year’s rod.

The spur system – From the rod which has grown away unchecked, select alternate buds on each side of the stem to produce short laterals. These bear fruit and should be stopped one leaf beyond. Then cut back each shoot to two buds in winter, one of which will form the grapes, the other the foliage. This will build up a system of spurs. Stop fruit-bearing laterals at the first joint after the bunch has formed, and pinch back non-fruiting laterals to 5cm (2in).
Vines growing horizontally against a wall should receive the same treatment as espalier pears. Cut back to the lower three buds in winter, the upper forming the extension shoot whilst the lower buds, one on either side of the stem, will form the lower arms. Train them first at an angle of 45°, tying them to canes, and then gradually bring them to the horizontal position. The following year, cut back the extension shoot again the three buds, the two lower ones facing in opposite directions to form the next pair of arms, about 40cm (16in) above the lower pair and so on until each vine reaches the required height. Each arm or rod should be treated the same as for the spur system.
When the fruit has set it must be decided how many bunches the vines can mature. This depends upon age. Probably the rods will carry ten bunches in their second year, twice that number next year and so on. Should there be overcrowding, nip out a few grapes with pointed scissors, as well as any damaged fruits.
Where growing under glass, a moist atmosphere is necessary for the buds to ‘break’. Syringe the vines daily to keep away red spider. This should stop when the fruits have formed and begun to show colour, otherwise they may decay. At this time, give ample ventilation so that moisture does not remain on the fruits. The grapes will be ready in late summer and early autumn.