Grapevines can be supported and trained to a variety of structures. In the home garden, structures range from the decorative arbor to the conventional trellis.
Construction of a grape trellis is similar to constructing a farm fence. The trellis must be substantial enough to carry the weight of the vines plus a heavy crop during high winds. Basically, the trellis consists of 1, 2, or 3 wires stretched tightly and secured to firmly set posts.
End posts serve as the anchor points as well as wire supports. End posts are generally 8 feet long, with a diameter of 4 inches, set approximately 2 feet deep in the soil. They may be braced in several ways. A common method is to set an extra post within a few feet of the end post. A heavy piece of wood or another post makes a good brace between the two end posts.
Line posts are also about 8 feet long, but with a diameter of 3 inches. They are set about 2 feet into the ground and are spaced about 24 feet apart within the row.
Galvanized wire is strung between the line posts. Galvanized wire is recommended because it is durable and does not cause serious wire chafing of young vines. Wire sizes commonly used include number 9, 10, or 11.
Wires are fastened to the line posts with ordinary staples. Wire placement is determined by the training system to be followed. For example, a Four-Cane Kniffin system would use 2 wires, one 3 feet high and the second 6 feet high. The Six-Cane Kniffin system requires 3 wires positioned 2, 4, and 6 feet above the ground. In the Single Curtain system, the single wire should be about 6 feet high.
Wires are secured to end posts in various ways. A common method is to wind the wire around the post once or twice and then twist the end several times around the wire as it is stretched to the next post. Some growers use special devices to attach the wires to the end posts because they simplify tightening of the wires. These devices employ cranks that eliminate removing the wires from the end post when tightening.
The best time to construct the grape trellis is during the first growing season. Tying new shoots to the trellis wires will allow for straight grapevine trunk development in future years.
This article originally appeared in the May 5, 1995 issue, p. 54.