Grapevine trellises provide the framework to encourage heavy vines and keep fruit off the ground, while allowing maximum sunlight exposure for plant health and decent fruit set. Since grapevines do not have clinging or twining capabilities, they need to be trained onto trellises. Choose a trellis type based on the growth habit and vigor of your grapevine cultivars, longevity of vines and cost of construction.
Factors
Picking a suitable trellis type is dependent upon that grape cultivar you grow. Some grape cultivars, such as imported European varieties (Vitis vinifera) possess upward growth habits. Others, such as native (V. rotundifolia) and hybrid grapes, have a downward or trailing growth habit. Many grapevines are particularly vigorous and require more substantial trellis systems to perform to their highest potential. Even though you can develop influential varieties on smaller trellises, pruning and training will be more pristine.
Single Wire and Double Curtain
Single-wire and double-curtain trellises are variants on the exact same subject. The single-wire construction is actually the least expensive layout. End articles, extending 5 to 6 ft above ground, are erected with single strands of wire stretched between them and also secured to each post. Double-curtain trellises allow twice the fruit production using two wires strung 4 to 5 feet apart from T-shaped supports. Double-curtain configurations are good options for grapevines with exceptional vigor. Wires must be stretched taut and stapled securely.
Geneva Double Curtain
The Geneva Agricultural Experiment Station at Cornell University developed the Geneva double curtain trellis system. Researchers determined that this layout provided much more sunlight exposure as grape leaf surfaces than in single-curtain systems. Like the conventional double-curtain trellis, the Geneva curtain uses two upper support wires, but it also adds a third lower cord. This wire, spaced 3 feet away from the bottom, supports the major back and reinforces vigorous vines. Upper wires are spaced 4 feet apart and 6 ft away from the ground.
Kniffen Systems
The four-arm or four-cane Kniffin process is one of the most popular trellises for crowd grapes. The University of Missouri Extension compares its layout to a two-wire fence. Two grape canes are trained in each direction along the lower wire, and two upper canes are trained similarly. The umbrella Kniffin system allows good air circulation and sunlight penetration. Canes are splayed out like the spokes of an umbrella, held atop the trellis construction. This system is most appropriate for vigorous cultivars.