Apple Trellis Construction for High Density Orchard Systems
In this video, we will discuss how to construct a durable trellis that will hold up to the stress of windy weather and heavy crop loads.
- [Instructor] A two dimensional high density apple training system, often referred to as a fruiting wall, provides many benefits to the fruit grower.
In this video we will discuss how to construction a durable trellis that will hold up to the stress of windy weather and heavy crop loads.
The tall spindle is one of the more common trellis systems, as it encourages fruit production in the second to third year after planting and the increased light interception within the canopy allows for high quality fruit production throughout the tree.
Because this training system relies on trees on precocious dwarfing rootstocks it is imperative that a support system be installed soon after planting the trees.
The success of your trellis will depend on your specific orchard site and system.
Variables to consider include your soil types, clay soils and dry soils resist failure better than sandy or wet soils, anticipated wind forces the trellis will need to withstand, and your canopy type.
In this example, a tall spindle fruiting wall.
These variables will determine which construction materials you will need, how to properly space and set your posts, and the spacing of your in-line posts.
There are interactive tools you can use to determine how the unique variables of your site will impact your construction.
One such tool can be found at trellx.com.
This website was developed through collaborative research between Washington State University, De Kleine Machine Company, and Steep Consulting and can be downloaded as a free spreadsheet.
Those specific site factors will impact your construction.
There are a few key engineering principles to use as a guideline.
Pressure treated wooden posts should be used for end posts and in-line posts and are also the strongest choice for tie-back posts.
End posts should be driven four feet into the ground using a hydraulic or vibrating post driver.
End posts should be five to six inches in diameter and post length will be determined by the desired height of the tree.
In-line posts should be four to five inches in diameter.
A five inch post is 50% stronger than a four inch post.
These posts should be driven three to four feet deep and spaced to a maximum of 30 feet apart.
The number of in-line posts you need per row will depend on the length of your row and on your topography.
A rolling site will require more posts.
Tie-back posts should be five to six inches in diameter, driven four feet into the ground, and angled away from the direction of the pull of the wire.
Wooden tie-back posts prevent trellis failure better than screw-in anchors.
If anchors are to be used they should be at least five feet long and have at least a six inch wide plate.
High tensile, class 3, 12.5 gauge galvanized steel wire should be used.
The wire should be spaced between two and two and 1/2 feet along the height of the trellis to have many places to secure the leader to the wire as it grows.
Keeping the leader securely tied will keep the leader growing upright, preserving its apical dominance.
Wires will be tensioned to 200 to 250 pounds.
Do not over-tension, as this will prematurely weaken the strength of the wires.
Trellis rows should be no longer than 500 feet.
If you are planting in an area where tree rows will be longer than this you will need to split up the rows into separate 500 foot sections.
In addition to strengthening your trellis, keeping rows shorter will make it easier for crews to move throughout your orchard block.
There are two options for securing wires to the posts.
The first is to use a hand drill to run the wires through each post.
Holes will be drilled parallel to the row for in-line and end posts and perpendicular through tie-back posts.
Alternatively, the wire can be attached to the post using two inch, nine gauge, double barbed, class 3 galvanized staples.
Staples should have slash cut points, as these will help prevent the staple from dislodging from the post.
Tie-back and end posts will be double stapled to help keep the wires in place.
For in-line posts two staples should be driven approximately an inch apart at a 45 degree angle forming a V on the post that the wire will be placed through.
Angle the staples so that they do not run with the grain of the wood.
This will help keep them from coming out of the post.
Now, let's go through the steps of constructing the trellis.
Using the principles we just discussed we will construct a four wire trellis with wires at 2.5, 5.5, 7.5, and 9.5 feet above the ground.
Having the top wire at nine and 1/2 feet will allow us to grow trees to a mature height of about 10 feet.
All posts will be set four feet deep using a hydraulic post driver.
We will be using pressure treated wood for all of our posts, including the tie-back posts.
For each row in this trellis we will use end posts that are six inches in diameter and 14 feet long.
Each row will need two tie-back posts six inches in diameter and eight feet in length.
Our in-line posts are five inches in diameter and 14 feet long.
In-line posts will be placed 30 feet apart in the rows.
We will be using the high tensile wire we previously described.
We will also use a spinning jenny wire dereeler for laying out the wire.
This will help reduce the risk of recoil or kinks developing within the wire, which would greatly weaken the strength of the trellis.
In this example we will drill holes through our posts for passing the wires, though we will discuss stapling as well.
On one end of the trellis wires will be wrapped around the tie-back post, which we'll refer to as tie-back post A, using either two crimp sleeves or a Gripple.
Three crimp sleeves can also be used to join wire rolls together.
Gripples can be retightened, making them a good choice, but there are many other fasteners and tightening tools available.
At the other end of the trellis, at tie-back post B, we will need in-line wire strainers and two crimp sleeves for looping off the wire.
You will need a Gripple and/or crimp tool and a wire strainer tensioner.
Trees will be attached to the wire using U clips.
You can use any other material that will keep the tree attached to the wire that allows room for trunk growth to prevent girdling.
Again, your materials and design may differ depending on your specific orchard conditions and what materials you have access to.
Before constructing your trellis be sure to take any necessary safety precautions.
High tensile wire can easily recoil, so it's important to wear gloves and eye protection when stringing your wires.
Wear tightly woven fabrics, long pants, and sturdy boots.
Ear protection and a hard hat is also suggested when setting the posts.
It is imperative that the leader of the tree remain straight and secure from wind forces, so you'll want to have your supplies well before planting time.
Construct your trellis shortly after planting to protect your young trees once they are in the ground.
Research shows the importance of keeping the leader tied as it grows.
Trees with weak growing leaders may also require a temporary inexpensive support in between wires.
You can also set your posts before planting your trees and then string a wire once they are planted.
Stringing a single wire as soon as possible can buy some time and you can also consider individual temporary stakes for your trees if trellis construction is going to be delayed.
To construct your trellis start by laying out the trellis rows.
Mark out the corners of the new planting site with stakes.
Using these as a reference, lay out a straight line between the corners and mark the sites of each trellis row with lime or spray paint.
These will be where you place each tie-back post.
Having marked the location of the tie-back posts posts should be angled about 10 degrees opposite the direction of the wires and driven into the ground using a post driver.
Driven posts will have the best contact with undisturbed soil, making driven posts 10 times less likely to pull out of the soil than posts set in augered or dug holes.
Posts should be sunk at least four feet into the ground.
Posts may be cut closer to the ground, though keeping them longer will make them easier to see, reducing the risk of accidentally running into them with machinery.
Next, mark the position of each end post in relation to the tie-back post.
The end post should be at least as far away from the tie-back post as it is tall.
The end post will be sunk four feet into the ground and should be angled away from the direction of the pull of the wires.
When deciding how much to angle your end posts and how far to place them consider the length of your posts, how far they must be set into the ground, and how much the angle will affect the vertical height of the post for positioning your top wire.
The ideal method is to think of the wire, end post, and ground as an equilateral triangle with 60 degree angles.
In this case, the distance between the tie-back post and the end post will be equal to the length of the end post that is sticking out of the ground.
However, if you wanna get your top wire to 10 feet this would require a 16 foot tall end post.
The most important thing is to sink the end post four feet vertically to the ground and to not put the end post too close to the tie-back.
For our trellis, since our post is only 14 feet and we wanted a wire at nine and 1/2 feet above the ground we were only able to tip it slightly away from the direction of our wire.
Once you have determined where to place and angle your end posts the smaller diameter end of the post should be driven into undisturbed soil with a hydraulic post driver.
Line posts should be spaced to a maximum of 30 feet apart.
The closer they are placed the stronger the trellis will be.
Pre-mark the location of each line post with a measuring line and mark it with lime or spray paint.
Marking ahead will ensure posts are evenly spaced and rows are straight.
Drive line posts four feet into the ground along the length of the line.
Drive the narrower ends of the post into the ground.
Measure and mark the heights where the wires will past through your end and in-line posts.
All wires will past through the same hole in the tie-back posts, which should be four inches above the ground.
Drill the holes for your wires.
Remember, holes for the tie-back posts should be drilled perpendicular to the direction of your wires, while end and in-line posts will be drilled parallel.
Position a spinning jenny wire dereeler near tie-back post A.
String the wire through the drilled hole at tie-back post A and fasten the loop with two crimp sleeves, a Gripple, or another fastener.
Starting with the bottom wire, string the wire through the end post and in-line posts.
Once the wire has been run the full length cut the wire at tie-back post B and place the end of the wire five to six inches into the ground.
This will keep the wire from springing back while you attach it to tie-back post B.
Alternatively, staples can be used to attach the wires.
Staple the wire to the back of tie-back post A four inches above the ground, and once again, tie off the loop with two crimp sleeves or a Gripple.
This should be double stapled, as the wire will exert a lot of force on the tie-back post.
Do not drive the staples home and leave enough space for the other three wires to fit through.
If using staples, staple the wires to the windward side of each end and in-line post.
Staples should be driven at 45 degree angle off of vertical to straddle the wood grain.
Staples that curve outward are much stronger than those that curve in.
To ensure they curve out rotate the staple 45 degrees off vertical away from the flat surface of the point on the upper leg of the staple.
The end post will also be double stapled.
As before, once the wire has been run the full length cut the wire at tie-back post B and place the end of the wire five to six inches into the ground.
To attach the wires to tie-back post B cut four three foot lengths of wire and pass the wire through the hole of tie-back post B.
Place the wire through the wire strainer, loop the wire, and then tie it off using two crimp sleeves or a Gripple.
Alternatively, you can double staple the loop to the back of the post.
Remember, do not drive staples home, as the remaining loops will also pass through it.
Place the cut bottom wire you have placed in the ground into the drum of the wire strainer and tension the wire to 200 to 250 pounds of tension using the wire tensioning tool.
Be sure not to over-tighten the wire.
If installing in the summer remember that the wire will contract during the winter and may need to be loosened.
Starting back from tie-back post A repeat these steps to attach the remaining three wires.
All wires will be attached at the same location on tie-back post A and B.
Attach and properly tension all wires near tie-back post B.
Be sure all end posts and tie-back posts have been double staple, as the wires tend to exert a lot of pressure at these points.
Attach trees to the wires using the metal loops or a similar fastener that prevents tree movement while allowing room for trunk growth.
Fasten the trees to the wires as the leader reaches them and attach your leader supports.
Your trellis should now be complete.
Planting intensive orchard systems to a trellis is a fundamental component of a successful blueprint for an orchard with the highest market quality and production efficiency.
For more information on establishing and training orchards visit the Penn State Extension Tree Fruit Production website.
If growing fruit trees is a new venture for you gather as much information as possible prior to planting an orchard and also consider taking a Penn State Extension course on commercial fruit growing.