Grapevines are heavy and large, with some growing up to 20 feet long. These climbers need support to lift them off the ground so they get the necessary amount of sunlight and air circulation required to produce healthy, succulent grapes. A grape trellis comprises of several posts in the ground with 12.5-gauge high tensile steel wiring strung between them. The young, delicate grapevine tendrils are trained to grow on the wires for support. A sturdy trellis allows you to harvest succulent grapes you can eat raw or use for jams, jellies and desserts.
Assess the area to determine appropriate spacing between posts. Each grapevine requires 8-by-8-foot of space to grow, so make sure you select an open area for the trellis. The climatic conditions of your area determine the height of your trellis. Short trellises are used in colder areas, while taller ones are used to support grapes in areas where temperatures during growing season are warm.
Select PVC pipes, aluminum poles or pre-treated wooden stakes for trellis posts. Make sure they are 3 to 4 inches wide, and stand 3 feet tall if making a short trellis, or 8 feet if making a tall trellis.
Use a post-hole digger or shovel to dig a 2-foot deep hole in the ground, as wide as the post. Lower a post into the hole, and backfill dirt around it so it is secure and does not wobble. This is called the main post. Depending on the number of grapevines you want to grow, space holes for main posts 20 feet apart.
Dig a hole for an anchor post in the ground, at an angle away from the main post. These posts support the wire and hold the grapevines in place. Insert an anchor post along each main post for a long trellis to provide sufficient support. If your trellis comprises of two to three main posts, an anchor post at each end will suffice.
Run a length of 12.5-gauge wire 3 inches above soil level, all the way along the length of the trellis. Attach it to each post with a staple gun before extending it to the next post. Repeat the procedure to attach a second length of 12.5-gauge wire along the trellis, but keep it a foot below the top of each main post. These wires are called support wires.
Insert large nails on both sides of the posts along both rows of trellis wires with a hammer. Cut several lengths of a lighter gauge wire and attach a chain link to each end. Hook the ends to each end of the trellis, with the wires resting on the nails in the middle posts. These wires, called catch wires, hold the grapevines in place.