_Influence of stocks on American grapes._
No doubt American species of grapes may be as profoundly modified by stocks as the European species, but there is but little evidence on this phase of grape-growing to be drawn from the experience of vineyardists. One rather conclusive experiment, however, shows that American grapes may be improved by growing them on stocks which give them better adaptations to their environment. The experiment was tried in the Chautauqua grape-belt in western New York by the New York Agricultural Experiment Station. The test was carried on for eleven years, during which time many interesting possibilities in grafting grapes in this region came to light. It was proved that the stock materially affects the vigor and productiveness of the vine and the quality of the grapes. The following brief account is taken from Bulletin No. 355 of the New York Station:
In this experiment a number of varieties were grafted on St. George, Riparia Gloire and Clevener stocks, and a fourth group on their own roots. The varieties grafted were: Agawam, Barry, Brighton, Brilliant, Campbell Early, Catawba, Concord, Delaware, Goff, Herbert, Iona, Jefferson, Lindley, Mills, Niagara, Regal, Vergennes, Winchell and Worden. The planting plan and all of the vineyard operations were those common in commercial vineyards.
Yearly accounts of the vineyard show that the vines passed through many vicissitudes. The experiment was started in 1902 when St. George and Riparia Gloire stocks from California were set and grafted in the field. Many of these died the first year. The winter of 1903-04 was unusually severe, and many more vines were either killed or so severely injured that they died during the next two years. The vines on St. George, a very deep-rooting grape, withstood the cold best. Fidia, the grape root-worm, was found in the vineyards early in the life of the vines and did much damage in some years. In the years of 1907 and 1909 the crops were ruined by hail.
But despite these serious setbacks it was evident throughout the experiment that the grafted grapes made better vines and were more productive than those on their own roots. As an example of the differences in yield, a summary of the data for 1911 may be given. In this year, an average of all the varieties on own roots yielded at the rate of 4.39 tons to the acre; on St. George, 5.36 tons; on Gloire, 5.32 tons; on Clevener, 5.62 tons. The crops on the grafted vines were increased through the setting of more bunches and the development of larger bunches and berries.