Controlling Shoot Vigor by Extending the Cordon Length and Increasing the Number of Shoots Per Grapevine.

This investigation was conducted with eight-year-old quadrilateral cordon trained Sauvignon blanc grapevines at Davis, California. The purpose was to determine how increasing the cordon length and number of shoots per vine, maintained at a constant shoot spacing of 15 shoots/m cordon length influenced the amount of primary and lateral shoot growth and canopy density. From a block of 50 vines spaced 2.4 X .36 m within and between rows, alternating vines were removed from vine rows to accommodate the large vines. The five treatments were: 4 m of cordon/vine (control), 4 m plus shoot trimming, 6 m, 8 m, and 12 m of cordon length per vine, each treatment replicated four times in a randomized complete block design. The cordons were extended in 1989 by training canes located at the ends of cordon branches to the desired lengths. The number of buds per vine corresponding to cordon lengths of 4, 6, 8, and 12 m were 60, 90, 120 and 180 respectively. The 12 m cordon length vines had primary lateral shoot lengths reduced by 19 and 37%, respectively, compared to 4 m cordon vines.