You must support grapevines above the ground so they can get adequate sunlight and water. Construct this sturdy support system that can hold a few vines in the back yard. When adequately supported, one grapevine can produce up to 20 pounds of grapes per year.
Choose the Site
Position your grapevine trellis in an area that gets at least 10 hours of full sunlight per day. Run the trellis in a north-south direction to maximize sunlight exposure time.
Check the Soil pH at the Site
The soil should have a pH of between 5.2 and 5.8. Soil pH slightly above or below these values will still promote healthy grape growth.
Plan the Layout
Plan a row of posts 20 feet apart at the centers for the trellis support frame. Calculate 6 to 8 feet of spreading distance for each vine, with 3 vines between each pair of poles. Mark the locations on the ground with grass-safe spray paint.
The posts should be 10 feet long. Two feet of each post goes into the ground for strength, with 5 feet above the ground. They can be 6x6 pressure-treated lumber, PVC or galvanized metal, either steel or aluminum.
At the start and end of each row, put 2 posts 10 feet apart, and attach a cross beam at 7 feet up to make an H support. This will keep the row wires from stretching and sagging. Use galvanized aluminum wire that is at least 12.5 to 14-gauge for the trellis.
Dig Post Holes and Erect the Trellis Frame
Use a post hole digger to scoop out holes 2 feet deep for each pole including the H-frame supports. When you install the poles, tamp the dirt in around them firmly. Check the row with a plumb line to ensure that they are straight up and aligned. Attach 4 rows of the galvanized wire with an industrial stapler, with the first row 18 inches off the ground to support the vine containers. The second row goes 18 inches above that one, and the top 2 rows 2 feet apart, at 5 and 7 feet. This will support the growing grapes at each stage of their development.
Get a helper to assist with tightening the wire to 250 pounds of tension, as measured with a wire strainer with a heavy-duty clip. During this step, wear safety glasses and sturdy gloves, as bits of the wire fly off in all directions as it is stretched and tightened.
Plant the Vines
Keeping the vines in their vine containers, plant 3 evenly-spaced between each pair of vine poles (not including the H-supports). The lowest level wire should rest on top of the vine containers to stabilize them. Train the first growth of each vine up to the second wire. They will need to be trained upward to the higher wires as they grow.
Protect the Vines from Animals
Enclose the whole vine trellis with a high fence and soft fencing wire pushed into the dirt at the bottom, to keep out rabbits, deer, and other wildlife.