How to Build a Grape Trellis
A simple way to create a grape trellis is by using a 2-wire system; I use this with cordon-trained vines. The use of a cordon implies growing the stem at an angle with a support for itself. I have the cordons on one wire that is just less than 5 feet in height; the second wire is about 14 inches above the first. As the plants grow and the shoots get taller, they ravel around the upper wire for support. Sometimes it is necessary to tie the shoots to ensure they do not sever.
The Posts for the Trellis
To break it down, there are only two different types of support that you will need for your vineyard. You will need large heavy posts that will support the wire and smaller, lighter supports that will support the actual vines. The heavy posts can be made from wood while the smaller supports can be made from wood or metal. Ensure that the wooden posts chosen are rot resistant; if they are not they will need to be treated. Be careful of what chemicals you use as it can leak off into the soil and disturb your vines.
Try to get heavy posts that are at least 3 inches in diameter. They should be suitable for rows up to around 280 feet long. If the rows will be longer than 280 feet then you will need thicker posts of 5 or 6 inches in diameter to compensate the extra weight.
Note that if the vineyard is in a location subject to strong winds then the heavy posts should be spaced close together. 15 to 20 feet apart is good in a windy location. The wind can easily cause the wire to lag, and so having the posts close together will prevent any leaning that could take place.
When you are working in average soil, you can set the heavy posts 2 feet deep into the ground. You will need to obtain posts that are around 8 feet in length to be able to leave 6 feet above ground for the trellis. If the soil you are using is softer or you are using sand, you should bury the posts deeper into the ground. In such a case, you should consider setting the posts in cement for a stronger bond to the ground.
Wire for a Grape Trellis
grape trellisGenerally the wire used for a grape trellis will be around 10-12 gauge. You can pick up the wire from any decent hardware store. The wire is usually sold in different size rolls and priced by its weight. One of the best wire types to use is high tensile stainless steel wire as it is protected against rust and does not give in by stretching at all. You can usually get away with using this wire for many years without the need to tighten the wire.
To get the wires to stay tight you will need to provide some kind of anchor to tie the wire to. Tying the wire to the posts will not give the support needed from the grape vines. Use an anchor to tie the wires to at the ends of the trellis. The anchors are dug into the ground to about 2 or 3 feet and have a loop at the top to tie the wire to. Set the anchors off at an angle leaning away from the posts to give a tighter pull to the wire.
Attaching the Wire
The easiest way to attach the wire to the posts is by drilling holes in the posts with a cordless drill. Drill holes in every post all the way down the trellis and feed the wire through, picking up the slack as you do. An alternative way to attach the wire is to hammer some large nails into the posts and tie the wire around the nails.
Supporting the Vines
As you have large posts to support the weight of the trellis you will also need to use smaller posts to support the vines. You can find good fence posts that would be used to build a standard fence in the hardware store; these are perfect to support the individual vines along the trellis.
The grape vines will begin to grow along the main wires, although you may need to do some finessing and place some of the vines along the trellis.
If the out site heavy posts start to lean inwards because of the weight of the vines then it is best advised to encase the heavy posts in cement into the ground.