Keith Striegler and Tammy Jones, University of Missouri
An excellent system for large sized vines, the Geneva Double Curtain or GDC trellis design consists of a horizontally divided canopy. The goal of the GDC system is to manage a dense canopy by dividing it in two, allowing more sunlight to reach the fruit renewal zone.
With this system, grapevines are trained from the trunk to bilateral cordons and pruned to retain short canes originating preferably in the lower 180 degrees of the cordon. Shoots are also positioned downward creating a canopy that has the appearance of two “curtains” on each side. Cross arms, usually four feet in width, separate the cordon support wires. This division in the canopy increases general exposure while reducing canopy density. Proper shoot positioning must be maintained to keep the canopies separated and to allow sunlight to reach the fruiting region.
Row spacing must be wide enough to permit mechanical operations. Generally a minimum row spacing of 10 feet is required. With the proper application, a GDC trellis system can result in yields that are higher than a single curtain trellis. The Geneva Double Curtain system can be more costly to establish than other trellis systems and the divided canopy must be properly maintained to achieve optimum yields and fruit of high quality.
Recommended Resources
Three Training Systems, Virginia Tech
Geneva Double Curtain for Concord Grapes, Cornell University
Divided Canopy Training Systems, Des Moines Area Community College
Reviewed by Bruce Bordelon, Purdue University
and Jim Wolpert, UC Davis