Quote:. . . forming an equilateral triangle . . . with the endpost, wire and ground is the simplest,
strongest, most stable and most effective form of anchorage.

Nuts and Bolts of Dwarf Fruit Tree Support Systems
Hugh W. Fraser1 and Darrel Oakes2
1 Ontario Ministry of Agriculture, Food & Rural Affairs, Vineland, ON
2LynOaken Farms, Lyndonville, NY

Presented at the 42ndAnnual IDFTA Conference, February 20-24, 1999, Hamilton, Ontario,
Canada.

There are many kinds of dwarf fruit tree support systems with numerous articles written about
their benefits.This paper focuses on the practical side of building a good support system.
Because growers want to know which system is more difficult or costly to build, a case study is
presented analyzing the overall costs on a per acre, or tree basis.

There are many support systems, each with variations.Support systems are often associated with
particular orchard systems.The most popular orchard and support systems are:
•Slender Spindle;midsize support posts at each tree and nothing else (Figure 1).
•Vertical Axis; narrow support posts at each tree, each connected to a single wire (Figure 2).
•Tatura Trellis; trees supported by three wires on an angle on each side of ‘Y-shaped’ canopy
(Figure 3).
•Super Spindle; trees supported by four wires one above the other, running the length of each
row (Figure 4).

SUPPORT SYSTEM COMPONENTS
There are five components to consider when building a dwarf fruit tree support system, all of
which are important in making sure that a tree support system will last for the life of the orchard:
•Soil
•Endposts and anchors
•Tree support posts
•In-line posts
•Wire

Soil Factor
A good dwarf fruit tree support system starts with a good soil foundation.Poor anchorage is the
main cause of failures.Consider the following:
•Clay soils offer more resistance to uplift and overturning than sandy soils.
•Dry soils offer more resistance to uplift and overturning than wet soils.
•Know where your tile drains are before you start installing posts.
•The higher the mature trees and expected apple weight, the more important is good
anchorage.
•Irrigation can loosen posts if too much water is applied, especially around anchor posts.
•Increasing the depth of posts in the soil by 33% increases a post’s strength by 100%.
•Undisturbed soil gives much better anchorage than soil that has been disturbed.
•Moving anchor posts because of rocks may compromise anchorage and headland space.

Endpostsand Anchors
Good anchorage of endposts for vertical axe, tatura trellis and super spindle is critical to the
success of all dwarf fruit tree support systems.Consider the following:
•The type and size of material is less important than the method of installation.
•Many methods are used, but the concept of forming an equilateral triangle (60oangles at each
corner with all sides the same length) with the endpost, wire and ground is the simplest,
strongest, most stable and most effective form of anchorage (Figures 2, 3, 4 and 5).
•Start by installing the endpost, leaning toward the headland, at 60oto the ground.An
equilateral triangle has about 1.75:1 sloped sides (Figure 5).That is, for every 1.75'
vertically, the endpost should be 1' horizontally.So, an endpost with the top 10' above
ground vertically should lean about 5.75' toward the headland of the row horizontally.
•For awire over the top of an endpost that is 10' vertically above ground, the screw anchor
(Figure 5) should be about 11.5' away from the endpost.
•A triangular template with 60osides is helpful for installing endposts at the correct angle.
•Pressure-treated lumber should be used for endposts to ensure they do not rot over time.
•Endposts that are pounded in with no starting hole are 50% stronger than augered ones.
•Custom operators to pound in posts are well worth their cost.
•Put the small end of round posts down for pounded posts, large end down for augered ones.
•Steel screw anchors are quick and cheap to install with specialized installation equipment.
•Screw anchors should be installed vertically, not angled, since this disturbs less soil.

Tree Support Posts
Tree supports are the most costly component of slender spindle and vertical axis systems.
Consider the following:
•Many types are used including steel angle bars, bamboo poles, pressure-treated posts and
galvanized electrical conduit.
•Although bamboo poles are least expensive, they are more difficult to push into the ground
than more expensive, but easier to install, steel angle bars or galvanized electrical conduit.
•Support posts must be larger in diameter and have greater strength for a slender spindle
system than for a vertical axe system because there is no wire to support posts in the slender
spindle system.
•Some growers install tree supports on the windward side of trees to prevent wind rub
damage.
•Plant the trees about 6" from the tree support posts.

In-line Posts
In-line posts give periodic support for the wire(s) in support systems for vertical axe, tatura trellis
and super spindle.Consider the following:
•They should be custom pounded for added strength.
•They are usually made from pressure-treated lumber.
•They usually range from 30 to 50' apart (10 to 15 m) depending on a number of factors, but
should be closer if the trees (and apple weight) are going to be quite high at maturity or if the
land is rolling, causing the wires to pull the in-line posts out of the ground.

Wire
Installing wire for vertical axe, tatura trellis and super spindle can be a time-consuming,
frustrating and dangerous job.Consider the following:
•Installation is usually at least a two-person job.

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The apple weight is the main load and it affects the sag of the wire.
Use 12.5 gauge high tensile strength wire.
High tensile wire springs and kinks when cut, so uncoil in reverse order.
Use an unwinding spool.
Consider distribution of the wire from a moving platform.
Install on the windward side of in-line posts.
Do not drive home staples, as this puts a stress point on the wire and weakens it over time.
Use gloves, safety glasses and be ready in case the wire breaks during tightening.

CASE STUDY
It is sometimes easier to compare costs when a case study is used (comparing “apples to
apples”).In this case study, slender spindle, vertical axis, tatura trellis,andsuper spindle
systems were compared (Table 1).Suppose a new orchard is being planted that is 5 acres in size,
500' long x 436' wide (the case study is not converted into metric to avoid confusion).Here are
the assumptions:
•Between-row spacing is based on 1.3 times the mature tree height, but is not less than 11' for
tractor access, and not more than 14'.
•Number of rows is based on allowing at least 14' between the last row and the side fence line
on the 436' wide orchard.
•Number of trees/row is based on allowing at least 25' clear turning room at headlands beyond
steel screw anchors, and planting trees between the post and screw anchors on wire systems.
•Pressure-treated wood may be more commonly available than galvanized electrical conduit
for tree supports, but conduit is used in this case study.

Material CostAssumptions
The costs of materials ($CAN) are as follows (Table 2):
•$2.65 for 2" x 8' pressure-treated wood tree supports, sharpened at one end (slender spindle).
•$1.75 for 10' hollow galvanized electrical conduit for tree supports (vertical axe).
•$0.02 for ties to attach trees to posts (slender spindle andvertical axe) or trees to wires (tatura
trellis and super spindle).
•$0.08 for twisted wire clips to attach tree supports to wire (vertical axe).
•$0.02 per foot of 12.5 gauge high tensile smooth wire (vertical axe, tatura trellis, super
spindle).
•$12 per 14' pressure-treated wood post anchor; 3" to 4" round, including staples (vertical axe,
tatura trellis, super spindle).
•$8.50 per 10' pressure-treated wood in-line post; 3" to 4" round (vertical axe, super spindle).
•$10.25 per 12' pressure-treated wood in-line post; 3" to 4" round, including staples (tatura
trellis).
•$10 per 8' pressure-treated wood cross brace, including bolts and nuts (tatura trellis).
•$9 per 4' x 3/4" x 6" plate steel screw anchor; includes tightening hardware (vertical axe,
tatura trellis, super spindle).
•Trees cost $6.80 each.

Labor Cost Assumptions
The costs for labor ($CAN) are as follows (Table 2):
•Grower labor at $10/hour to install wire, tree supports, ties, wire clips, braces, etc.
•Custom post pounder at $45/hour to install post anchors, screw anchors, in-line posts.
•Labor costs include moving around orchard for installations.