There are as many trellis designs as there are snowflakes in the universe. The problem can be picking one out that suits your needs. Luckily we have some guidance in that area. Not only is there people with decades of experience here but our climate is very similar to the Willamette Valley to the south. Our state is dominated by the hot, arid Eastern part of the state and what works over there, is not the best way to train grapes on the cooler Western side of the state.
Let start with what works in Oregon and compare it to what they do in Eastern Washington state and why that doesn’t work for us. Also, I want to say this is for wine grape for the most part, but will work for table grapes too but table grapes can have a higher degree of variation due to their natural disease resistance and earlier ripening characteristics. In most of Burgundy, growers are dictated by law on how they can prune their vines (which is hard to believe). The vines must be 1x1x1 meter apart. This system of training probably hasn’t changed much in hundreds of years. Most growers use what is called a single Guyot system of training, which is one cane from last year laid down on a wire and held in place with a twist tie. There is a double Guyot system, which is two canes laid in opposite directions and if you are spacing further than 4 feet apart in a row, you will probably want to use this.
The Guyot pruning system matches well with the Vertical Shoot Positioning systems. The new shoots grow from buds in the canes upwards and need to be contained in the VSP system of wires. Generally, in the Puget Sound (as is in Oregon), we will do a 4 foot spacing of the vines in the row and 6-7′ spacing for the rows. The height of your trellis should be the same as your width between rows for optimal utilization of space and sunshine. It depends on how much land you have and your equipment. Backyard vineyards can go really close. If you are a backyard grower, you might opt for a higher trellis system if you only have one row.
The VSP is made up of end posts, wires, chains, middle posts. Usually one wire on the bottom that is where the canes are tied too, then 3 sets of catch wires above that the vines grow up into. They are called “moveable” because they can usually be pulled off. This is just so it aids you in the positioning part and usually don’t move up or down. The big debate is on the height of the bottome or “fruiting” wire. In Burgundy, it’s around 12″. In Oregon, it’s anywhere from 24-36″. The height is dependent on how cool you are. Generally the cooler it is the lower you go, but it has it’s limits. Too low and you get dirt and splashing and animals eating your grapes. In the Puget Sound, most people do 18-24″ inches above the ground.
The way they train vines in Eastern Washington is sometimes called a sprawl or California sprawl. Essentially, it is a high wire at about 4 feet above the ground and maybe on set of catch wires above this is V shaped. Usually there is a way for the western side of the wires to be let down lower later in the summer. They have two things going for them that are different than Oregon and Western Washington and that is lack of rain and sunshine. They have to drip irrigate, there is no way around that for them. We are mostly dried farmed and rely on ground water. Drip irrigating means you can control the growth very tightly. Secondly the sunshine in the afternoon can be so intense it can burn the fruit so they have to shade it most years. They do that by letting the canopy hang over the wire shading the fruit in the afternoon.
As for the actual materials to create a trellis. It is usually made up of:
- End Posts – Either wood or metal. For commercial growers, you will want 4″ or bigger or steel posts. Usually driven into the ground at and angle or upright.
- Line posts – Same as end posts but smaller. You can get away with T Posts in smaller vineyards.
- Wire – Two types of wire usually. 12.5 gauge high tensile wire for the canes. Needs to be strong. 14 gauge low tensile (bends easy) wire for catch wires.
- Tensioners – I use ratchet type tensioners for the fruiting wire
- Chain – metal chain for the ends of the catch wire
- Nails or Hooks – to hold wire in place on the end posts and line posts
- Earth anchors – If you are angling your end posts, you will need to drill these into the ground
- Spinning Jenny – you will need one of these to reel out your wire so it doesn’t coil up on you
Some caveats for backyard growers – You will not need to go through this much trouble for just a few vines. You might get away with smaller posts because the forces aren’t as much. You might be fine with just 14 gauge wire, but the basics are the same. You want to grow your vines up between some wires to keep the growth in an upward trajectory.