Trellis systems nc state extension publications grade 9 electricity module

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.

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 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)