The treatment of vine rods during the winter is important for the production of good quality clean bunches of fruit. They should first be untied from the wires and all aerial roots trimmed off. The rods should then be pruned. Grape vines are usually trained to one or two rods, that is, main stems, along the full length of which there are fruiting spurs. In their first season all side shoots should be cut back to within two buds of their base. In subsequent seasons, shoots which arise from these buds should be cut back each winter to one or two buds. The position of the cut depends on the direction in which the bud is pointing. The cut should be made immediately above a bud that points away from the rod. Having pruned the rods in this way, all loose bark should be scraped off and the rods painted with Gishurst compound as a disease preventative.
Early in the year the vine rod may be started into growth by giving heat, but if no heat is ‘available it will break into growth naturally towards the end of March. In the early part of the season the ventilator should be opened slightly in the morning and should be closed by about three-thirty. This will preserve the sun heat. The amount of air given each day can be increased as the weather improves, but care should be taken to avoid draughts especially in windy weather. If ‘the current of air is not thus’ regulated, the leaves and fruit will become mildewed. Control the temperature in this way so that the house is at all times about 55 degrees Fahrenheit.
Even when pruned to only one visible bud each spur generally produces several shoots. When these are a few inches long all but the strongest should be removed from the base.
Vines require syringing once a day with water, preferably rain water from a tank. In a heated house the pipes, too, should be damped. As soon as the flowers appear, syringing should cease, but may be continued for a few days when they have set. Syringing should not be continued for long after this period or a deposit will be left on the fruit.
To assist the fruit to set, the, wires supporting the vine rod may be tapped gently and this will release a certain amount of pollen. Midday on a warm sunny day is the best time. The ro’ds require constant attention in the matter of training. As soon as the flower clusters appear, all the shoots should have their growing points pinched out two leaves beyond the flower cluster.
As a result, further shoots will grow and these should be stopped after the first leaf. Eventually, only one bunch of fruit should hang from each shoot, the best being selected and others cut out.
A mature vine rod can carry eight bunches. The fruit in each bunch will require thinning in order to obtain good-sized berries, and for this purpose a pair of pointed scissors is used.
Avoid touching the berries with the hands or head while working, as this can cause the skins to become brown. A thin stick or split label will help to hold the berries while thinning, and with a little practice is easier to use than the fingers. At the first thinning the smallest berries are removed; seedless berries will never swell and can be cut away at once. Later remove misplaced berries; by this time it will be seen that some berries are being squeezed; all these must be cut and space left for all the remaining berries to develop. The shoulders must be left full to give the bunch the correct shape; on larger clusters the top two or three sprays which will form the shoulders may be lifted and tied loosely to the wires.
Varieties. Early and mid-season Black Hamburgh, Madresfield Court; black.
Late: Black Alicante, Muscat of Alexandria; the choicest green.