Geneva double curtain, often abbreviated to GDC, a vine-training system whereby the canopy is divided into two pendent curtains, trained downwards from high cordons or canes. The system was developed by Professor Nelson shaulis of Geneva Experiment Station in upstate New York in the early 1960s. The vines are planted in about 3-m/10-ft rows and the trunk divided at about 1.5 m height to form two parallel cordons about 1.3 m/4 ft apart. The foliage is trained downwards from these cordons, forming the so-called double curtains. This training system was one of the first examples of a divided canopy developed in the New World and, by reducing shade, it increases both yield and grape quality (see canopy microclimate). While initially developed for the American variety concord, the system has been applied to vinifera wine grapes, especially in Italy. It was one of a number of trellis systems advocated as part of canopy management in the 1990s. The GDC system is particularly useful for wide row spacing vineyards of high vigour. While most wine grape varieties have more erect shoots than the American vines it was developed with, it has been found suitable for use in many vineyards, and some notable increases in yield and wine quality have resulted from use of the system.