What can you tell me about trellising raspberries?

Answer: Although some cultivars are upright in growth habit and can be grown without a trellis system, most bramble fruits benefit from the additional support. The goal of a trellis system is to keep fruit off the ground, allow for good light penetration and air circulation throughout the canopy, and assist in ease of harvest. These factors will contribute to a healthier bramble planting with higher productivity and more efficient harvest. For organic growers, ensuring good canopy management is key to reducing disease and pest incidence. And because trellising allows for easier access to fruit, cleaner picking is possible, resulting in fewer overripe berries—which also lessens the attraction to picnic, sap, June, and Japanese beetles (Fernandez et al., 2016).

When selecting a trellis system, important considerations include cost of materials and construction, availability of labor, and regional climate. Treated lumber is not allowed in organic production and alternatives to treated-wood posts must be found. More information appears in the ATTRA publication Pressure-Treated Wood: Organic and Natural Alternatives. Researchers at North Carolina State University have estimated the cost per acre of various bramble trellis systems (Safley and Fernandez, 2011). With their cost assumptions, a V-trellis with metal posts costs $3,960 per acre, a T-trellis with wooden posts comes to $4,623 per acre, and the Shift Trellis comes in at $5,740 per acre.

The most common trellis systems for bramble fruits include the V-trellis and T-trellis, which both provide two sets of wires at two heights to support the canes and allow for an open canopy in the middle of the row. Materials used for these systems usually include wooden posts, steel posts, and wire, with metal or wooden cross-arms being an additional component of the T-trellis (Fernandez et al., 2016). Detailed information on trellis systems can be found in the resources listed at the end of this publication.

The Shift Trellis and Rotating-Cross-Arm Trellis are new trellis systems that have been designed for floricane-fruiting blackberries to increase productivity and ease of harvest, and allow for protection from winter injury in northern climates. The trellis arms pivot on an axis that allows for cane manipulation to induce fruit formation on one side of the trellis arm, which permits fruit to ripen in the shade. These systems are costly to install and require additional labor for management, but the current results appear promising (Takeda et al., 2013).

Ready to learn more? Check out the ATTRA publication Brambles: Organic Production. This publication focuses on organic practices for blackberry and raspberry production. It discusses cultural considerations including site selection, establishment, pruning and trellising, and it introduces organic practices for fertility, weed, disease, and insect management. It also provides new information on greenhouse production and season extension and addresses economics and marketing.

References:

Fernandez, G.E., E. Garcia, and D. Lockwood. 2016. AG-697. North Carolina Cooperative Extension Service. North Carolina State University. Raleigh, NC.

Safley, Charles D., and Gina E. Fernandez. 2011. North American Raspberry and Blackberry Conference. Savannah, GA. January 6.

Takeda, F., Glenn, D.M., and Tworkoski, T. 2013. Journal of Berry Research. Vol. 3, No. 1. p. 25-40.