NC State Extension Publications

 

Trellis systems are used for cane support with trailing and semi-erect cultivars to keep the fruit off the ground and with erect cultivars that will be allowed to grow tall before being topped. Positioning canes on a trellis improves sunlight exposure, air movement, and spray penetration throughout the canopy. Using a trellis system will make the planting easier to manage. Easier harvest results in cleaner picking, lessening the attraction of picnic, sap, June, and Japanese beetles that can result from the presence of overripe and rotted fruit. Trellising can also make floricane removal easier. Construct trellises prior to the first harvest season.

Growers use a variety of trellis support systems to support canes. Your trellising goal is to minimize labor and maximize yield. Each trellis type has its advantages and disadvantages, and most can be modified according to your needs. Evaluate each trellis system to determine what type best suits your needs.

Many different types of trellis systems exist. Consider the following factors when selecting which type to use: cost of materials and construction; availability of competent, trained labor; and climatic considerations, such as the potential for cold injury.

Line posts are used to position wires at desired heights above the ground. Posts can be either wood or metal. Wood line posts stand up to stresses—such as wind perpendicular to the trellis—better than metal posts. If wood posts are used, they should be treated for in-ground use. Unless heavy metal posts are used for line posts, it is advantageous to use a wood line post every second to third post. Drive or set posts 2 feet into the ground with 5 feet remaining above ground. Wood posts should have a top diameter of about 4 inches. For hand harvested crops, set posts no more than 25 to 30 feet apart. The end posts, where wire tensioning is done, should be larger than line posts (suggest a minimum of 8 feet in length with a 6 inch top diameter to allow them to be driven 3 feet into the ground). Generally, wood is used for end posts. Use anchors to further support end posts.

The top wire on the trellis is the load-bearing wire. Use a 1212 gauge high tensile electric fence wire. The lower wires are for cane positioning and do not need to be as heavy. A 14 gauge high tensile wire should be adequate.

I-Trellis

The I-trellis can be a single wire or two wires spaced apart and secured to posts at 2 and 4 feet above the ground (Figure 15). Posts can be metal or wood treated for in-ground use. They should be set at least 2 feet deep and be spaced about 25 to 30 feet apart. Secure canes loosely to the wire or tuck them in between the two wires. This trellis is relatively inexpensive and easy to build. Yields may be lower than with other trellis designs. The canopy can become crowded, resulting in added disease pressure, more difficulty in harvesting, and potentially poorer fruit quality.

Figure 15.

Figure 15. I-trellis (Hedgerow): use 6- to 8-foot metal fence posts, cedar posts, or pressure-treated posts (4 to 6 inches in diameter) spaced about 25 to 30 feet apart. Bury posts 24 inches in the ground.

V-Trellis (with Metal T-Posts)

The most common type of caneberry trellis is the V-trellis (Figure 16a and Figure 16b). The typical V-trellis design has steel posts set 20 to 30 degrees from vertical.

Figure 16a. V-trellis for blackberry or raspberry support.

Figure 16a. V-trellis for blackberry or raspberry support.

Figure 16b. V-trellis.

Figure 16b. V-trellis.

Gina Fernandez, NC State University

California V-Trellis

The California V-trellis is a modification of a system developed in Norway, called the Gjerde system. In the winter, the 1-inch by 1-inch moving posts are tied nearly vertical (Figure 17a). When the buds break in the spring, new fruiting laterals on the floricanes are encouraged to grow outward (Figure 17b).

Video on the California V-Trellis.

Figure 17a. California V-trellis (with wooden posts) pre-bloom.

Figure 17a. California V-trellis (with wooden posts) pre-bloom.

Figure 17b. California V-trellis (with wooden posts) Post-bloom.

Figure 17b. California V-trellis (with wooden posts) Post-bloom.

Figure 17c. California V-trellis.

Figure 17c. California V-trellis.

Gina Fernandez, NC State University

T-Trellis (with Rebar)

The T-trellis is a divided canopy design where floricanes are secured to wires on either side or both sides of the trellis, creating room for primocanes to grow upright between the wires (Figure 18a and Figure 18b). The main post is made of 12-inch rebar while the cross arms are 38-inch rebar. Because primocanes and floricanes are separated in the canopy, more sunlight can reach the developing crop. Harvest and floricane removal following harvest are easier due to the separation of floricanes and primocanes. This type of system is suitable for primocane-fruiting raspberries.

Figure 18a. Rebar T-trellis.

Figure 18a. Rebar T-trellis.

Figure 18b. Rebar T-trellis.

Figure 18b. Rebar T-trellis.

Gina Fernandez, NC State University

T-Trellis (with Wood)

This trellis functions similarly to the rebar T-trellis, but it is made of wood (Figure 19a and Figure 19b). Set 8-foot posts made from pressure-treated lumber or cedar 2 feet into the ground. Use 2-inch by 4-inch pressure treated lumber for cross arms. Set posts 20 to 30 feet apart in the row.

Figure 19a. Wood T-trellis.

Figure 19a. Wood T-trellis.

Figure 19b. Wood T-trellis.

Figure 19b. Wood T-trellis.

Gina Fernandez, NC State University

Shift Trellis and Rotating Cross Arm Trellises

Both of these trellis systems move the position of the canes during the year. In the early spring, the trellis is moved to a horizontal position. Once the flowering shoots have begun flowering, the canopy is moved beyond the vertical position for harvest. In both of these systems, fruiting occurs primarily on one side of the trellis. Both systems require intensive management of the primocanes.

The shift trellis is made of wood and pivots in an arc from one side of the row to the other (Figure 20a and Figure 20b).

Video on Shift-Trellis.

Commercial rotating cross-arm trellises are constructed of fiberglass reinforced plastic components manufactured by the pultrusion process.

“The trellis consists of a post (∼50 cm) (a) which has two plates (b) attached at the top (Figure 20c). A long (c) and a short (d) cross-arm are secured between the two plates with detent pins. Both cross-arms are rotatable. There are two cane training wires (e1 and e2) that are threaded through holes in the plates. Additional trellis wires (f) are threaded through both cross-arms and secured to end trellis assembly arms. The wires in the foreground are connected to a wooden tie-back post (g). The primocanes are placed on the training wire below the short cross-arm (e1). Wires terminate at the wooden tie-back post and on end trellis assembly arms on the first and last posts of each row with a “Quik-End” tensioner (h) which has internal spring-loaded clamps. In winter, the canes are pushed over to the training wire under the long cross-arm (e2).

“When plants are in bloom, the long cross-arms are oriented horizontally (Figure 20d). Note the top of the post (arrow) on left side. The lateral canes that were secured to the wire on the long cross-arms have produced flower shoots and all have grown upward. Flower shoots that develop from axillary buds oriented down on the lateral canes will curve and grow upward between lateral canes. Soon after all the flower shoots have a few open flowers, the cross-arms can be rotated upward and beyond vertical. By this time, the rachis (inflorescence axis) is woody and will not curve upward. The upward rotation of the cross-arms positions the fruit on one side of the row.” (Takeda, Glenn, and Tworkoski 2013, 24-40)

Figure 20a. Shift trellis.

Figure 20a. Shift trellis.

Graphic courtesy of Virginia Technical University, http://scholar.lib.vt.edu/mirrors/vaes/vaes99-1.pdf.

Figure 20b. Shift trellis.

Figure 20b. Shift trellis.

Gina Fernandez, NC State University

Figure 20c. Rotating cross-arm trellis.

Figure 20c. Rotating cross-arm trellis.

Figure 20d. Blackberry plants on the rotatable cross-arm trellis

Figure 20d. Blackberry plants on the rotatable cross-arm trellis at bloom.

 

Table 5. Advantages and disadvantages of each type of caneberry trellis system.
Trellis Type Advantages Disadvantages
I-Trellis
  • Easy to build and maintain
  • Economical
  • Lower yield
  • Crowded canopy increases disease pressure and makes harvest more difficult
V-Trellis (with metal T-posts)
  • Allows greater light penetration into the canopy; higher yields than a single post
  • Air circulation is greater; decreased disease pressure
  • Using fence posts, horizontal wires can be moved up or down to accommodate a cultivar’s vigor
  • Higher cost than a simple I-trellis
California V-Trellis
  • Fruit develops on outer parts of canopy enabling easier harvest
  • Increases light and air circulation in canopy
  • Labor intensive and expensive
  • Sprayers can knock off blooms
  • Spray penetration not great when canopy is closed.
T-Trellis (with rebar)
  • Posts can be reused and are therefore economical
  • Easy cane removal after harvest
  • Allows greater light penetration into the canopy; higher yields than a single post
  • Air circulation is greater; decreased disease pressure
  • Cannot be higher than 4 feet; some potential yield is forfeited
  • May not be able to support heavy crop load
  • May not hold up in ice storms
T-Trellis (with wood)
  • Opens canopy for higher yields and improved air circulation
  • Can retrofit from an I-trellis without having to install new posts
  • Wire height cannot be adjusted once cross arms are installed
  • Wires set too high establish fruiting zone beyond reach of labor
Shift Trellis and Rotating Cross Arm Trellis
  • Easier harvest; all fruit is on one side of the canopy
  • Less sunscald on fruit
  • Can be covered in winter to minimize cane injury
  • Expensive
  • Harder to learn how to train and prune

Authors:

Extension Specialist (Small Fruits)
Horticultural Science
Professor
University of Arkansas
Professor
University of Tennessee

Publication date: Nov. 2, 2015
AG-697

North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, veteran status or disability. In addition, the two Universities welcome all persons without regard to sexual orientation.