UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION CIRCULAR No. 249 June, 1922 REPLACING MISSING VINES By FREDERIC T. BIOLETTI Regularity of the vineyard is essential to economical, maximum production of the best grapes. Two necessary factors of regularity are a perfect ''stand" and even size and vigor of the vines; that is, every vine should be growing and should be equally capable, under the same treatment, of bearing grapes in competition with its neigh- bors. The best way to reach this condition is to develop a perfect stand of even vines the first year, a degree of perfection seldom reached even by the most skilful and experienced growers. If 95 per cent of the vines planted grow it is considered excellent ; 85 per cent is nearer the average even in good vineyards ; and much lower per cents are common. Where vines are missing the first year, new vines are planted the second. The cost of planting these vines is high, they are more troublesome to take care of, they grow less vigorously, and a larger proportion of them fail. After the second year, replanting becomes increasingly difficult and uncertain. Replants after the second year are always dwarfed and many growers doubt whether they pay for the work they make. Some growers believe that the loss from a missing or dwarfed vine is made up by increased crops on the adjoin- ing vines. The compensation for a dwarfed vine is in whole or part neutralized by the cost of handling a small vine, which is nearly as great as that of a large one. Moreover, irregularity in the size of the vines increases the cost and difficulty of proper pruning and culti- vation. The extent of the compensation for missing vines may be estimated from observations made in the experiment vineyards at Kearney and at Davis. 2 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Muscat (144 vines five years old) at Kearney — Crops of 1915-16: Mean crop of vines between two vines 27.8 lbs. Mean crop of vines next to a vacancy 30.6 lbs. Mean crop of vines at end of rows 30.7 lbs. Sultanina (240 vines seven years old) at Davis — Crops of 1916-17 : Mean crop of vines between two vines 28.6 lbs. Mean crop of vines next to a vacancy 34.8 lbs. This indicates that the loss of 27.8 lbs. due to a missing Muscat was partially made up by an extra crop of 5.6 lbs. on the two neigh- boring vines, a compensation of about 20 per cent. The loss of 28.6 lbs. due to a missing Sultanina was compensated to the extent of 12.4 lbs., or about 43 per cent. With weak varieties the compensation is less because they are less capable of utilizing the extra space. For a similar reason the wider the spacing, the less the compensation. The compensation will undoubtedly increase as the vines become older but will probably never be complete unless the vines are planted much too close. Where two or more vines are missing in adjoining spaces, the compensation will of course be less. If we accept the results of the weighings at Davis and Kearney as typical, the loss on a Muscat vineyard with a normal crop of 6 tons per acre is about 960 lbs. per acre for every 10 per cent of missing vines, and about 680 lbs. in a similar Sultanina vineyard. The loss from the dwarfed vines that result from most replanting and the corresponding compensation from their overgrown neighbors can only be estimated. Both loss and compensation would probably be less than with missing vines, though possibly the net loss would be nearly or perhaps quite as great, if we consider the cost of handling the small vines. In some cases it is possible to replant missing vines perfectly at any age by the method of layering. This can be done easily only in a trellised vineyard. Two ways of applying this method in an Emperor vineyard grown on the cordon system are shown in the photographs. Photograph A shows a long vigorous cane (c) reserved for the purpose on a vine adjoining the vacant space (o). This cane is to be placed in the ground as soon as the conditions for growth are favorable, late in March or in April. Two ways of doing this are shown by photographs B and C. Circular 249] REPLACING MISSING VINES TIT Replanting a cordon by layering. A, cane (C) reserved for layering; B, direct layer — growth the first year (NV) ; C, reversed layer — growth the first year (NV). 4 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION In the case shown by B the reserved cane (w) was bent down to a trench about 10 inches deep and carried along the bottom of this trench to the place of the missing vine. There it was bent up at a sharp angle and tied to the stake, where it was cut off, leaving only one bud above the ground. N V is the new cane which grew from this bud during the first summer. It is larger than the original cane and reaches well beyond the next vine. In the case shown by C the reserved cane (w) was simply cut to a suitable length and planted in a reversed direction in the place of the missing vine. The new cane (N V) which grew the first year is strong and healthy but smaller and less vigorous than that of case B. The method shown by B gives the best results. A reversed layer should be used only when it is impossible to get a cane sufficiently long for a direct layer. The direct layer gives a better shaped trunk and develops more rapidly. The reversed layer will make more growth the first year if a wire (w) is placed around the cane just behind the bud that it is desired to develop. As the cane increases in thickness, the pressure of this wire prevents the passage of food from the leaves into the old vine and directs it into the roots of the new vine. The original cane will then remain small as in B, instead of increasing as shown in C. The only care needed by these layers during the growing season is to prevent all growth on the layered cane except the single shoot reserved for a new vine and to carefully tie up this cane to give it the desired form. No buds should be allowed to grow on the cane between the nurse vine and the ground. The new vine is separated from the nurse vine after the second year's growth. With the direct layer, the separation is made below ground at the point indicated by an arrow; with the reversed layer, at the points indicated by the dotted lines. The new vine produced from a layer should be allowed to bear little or no fruit the first year and the crop should be limited the second year. The vine is thus enabled to devote all its energies to growth of stem and root and by the third year it will be able to com- pete with its older neighbors on equal terms.