Feasibility of Shift Trellis Use for Northeastern Blackberry Production

Project Overview

Project Type: Farmer
Funds awarded in 2011: $3,318.00
Projected End Date: 12/31/2014
Region: Northeast
State: Pennsylvania
Project Leader:
Roy Brubaker
Village Acres

Annual Reports


  • Fruits: berries (other), berries (brambles)


  • Education and Training: on-farm/ranch research
  • Farm Business Management: budgets/cost and returns, feasibility study
  • Pest Management: cultural control
  • Production Systems: organic agriculture

    Proposal summary:

    Bramble crops such as raspberries and blackberries are an important source of income for many small- to mid-size farms. Outside of California, Oregon, and Washington, there were 4,573 U.S. farms with blackberries in 2007 and 5,469 farms with raspberries, each farming just under an acre of brambles each on average (USDA, 2007). This means that nearly ten thousand farmers are using bramble crops as part of what is likely to be a highly diversified, locally-marketed farm operation, since an acre of brambles is not enough to provide a farm income on its own and most wholesale and processing bramble fruit is produced in the Pacific Northwest (Kuepper et al., 2003). Brambles are ideal candidates for marketing through local food systems – they have a short shelf life, limiting the distance they can be shipped (Kuepper et al., 2003) and fetch high prices at farmer’s markets and in restaurant sales. Both our own CSA customers in central Pennsylvania and the organic grower’s cooperative we belong to (Tuscarora Organic Grower’s Cooperative) are routinely willing to pay $2.50 a half pint for organic red raspberries in whatever quantity we can supply. Our experience suggests that consumers treat bramble fruit as a luxury “snack” purchase, rather than a staple food crop, making the price highly elastic. Brambles are less expensive to establish than tree fruit, easier to grow organically, and produce a quicker return on investment, but have many of the same soil conservation advantages as other perennial crops.

    However, brambles still require a large amount of labor at harvest time, which smaller growers may have difficulty hiring, managing, and paying for before the crop is sold. Demchak (2009) estimates that one acre of summer-bearing red raspberries will cost $6000 in labor to harvest, a substantial expense for a small operator. Thorny new primocanes grow towards sunlight on the edges of plants, interfering with harvesting. Bramble fruit are also prone to Botrytis mold when wet, reducing the number of salable fruit. Shift-trellis systems such as those proposed by Stiles (1995, 1999) promise to help overcome these limitations, but they have not been tested extensively on small farms. By shifting the configuration of the supporting trellis during the growing season, after the initial bloom but before fruit have finished developing, shift-trellis systems aim to present a wall of easily accessible fruit projecting onto only one side of a bramble planting. If successful, they should substantially speed up harvesting by keeping all the fruit together and away from the thorny new growth in the center of the row.

    Exposing the fruit in this way should also improve air flow around both the berries and the entire plant, limiting the danger posed by fungal molds such as Botrytis. Although these trellis systems are more costly to construct than the more traditional stationary trellises, increases in harvesting efficiency and the percentage of saleable fruit could more than make up for these initial costs, especially for plantings that produce for ten or more years.

    Shift-trellis systems for bramble crop production were originally developed in the mid-nineties as a way to improve fruit quality and harvesting efficiency, but despite their recommendation in several extension publications nationwide, they have not been widely adapted by smaller producers. Reasons for that may include their increased initial costs to install and the lack of field trials testing their benefits. Nevertheless, if such systems work as expected, they could greatly improve the profitability of bramble production for mid-size producers – especially in blackberries, where dangerously thorny canes can greatly reduce picking efficiency under conventional trellises. We propose to test such a shift-trellis system against a conventional trellising on our 30-acre mixed vegetable farm in Central Pennsylvania, measuring fruit yield, quality, and harvesting efficiency over the first three production years of our new blackberry planting. Our results will help other bramble producers decide whether these new trellis systems are a worthwhile investment on their own farms.

    Project objectives from proposal:

    The experiment will take place on our farm in Mifflintown, PA (40.5º N, USDA Zone 6a). We currently have four 175-foot rows of first-year ‘Kiowa’ blackberry plants and one row of ‘Prime Jan’ blackberries planted 12 feet apart in roughly E-W rows following the contour of a north-facing slope. Two of the ‘Kiowa’ rows, and the ‘Prime Jan’, will be trellised using conventional T-shaped posts and wire, to function as controls. Two rows of ‘Kiowa’ will be trellised using the LARS trellis style. Although we could achieve greater replication with a split-plot design, where each row of plants included several types of trellis, the added expense and complication involved in squeezing various end posts in between plants and manipulating them throughout the season do not seem worthwhile to us. Each individual row contains roughly forty-five plants and covers 175 feet of ground, so we do not expect between-row environmental variation to be substantially greater than within-row variation.

    In early spring each planting will be fertilized with 20 lbs of feather meal (13% N) along each 175’ row, then applying 1-2” grass and leaf compost in a 2’- wide band over the row. Post bloom, each row will be fertigated as necessary with any additional nutrients, based on foliar analysis. If plant vigor is lacking, we may also apply liquid kelp or fish as a foliar spray. Weeds will be controlled by mulching in rows and mowing sod strips between rows; our past experience with raspberries suggests that occasional hand-weeding may be necessary in this system but that most weeds are adequately controlled this way.

    Trellis systems will be constructed in spring 2011, to ensure adequate time to train this year’s canes to them. We plan to build a LARS-style one-sided shifting trellis, with small modifications in order to better make use of the materials we have on hand already. Our LARS trellises will have a post every 25 feet along our rows, for a total of 2 endposts and 6 mid-row posts in each row. Each post will consist of an eight foot section of untreated (for organic certication rules) locust, driven at least three and preferably four feet into the ground, attached to a 6-foot length of pipe 10 inches above ground level with a 8” carriage bolt. This pipe will form the swinging part of the shift trellis, and be further attached to the wooden post with a 54” length of flat steel to serve as a brace. The steel brace will have several holes in it, allowing it to be swung into place so that it can brace the swinging arm in both the horizontal (pre-bloom) and near-vertical (post-bloom) positions. We feel that this steel brace will add needed stability to the structure that Stiles’ original LARS design lacked in its use of a length of chain looped around the joint between the two pieces.

    The endposts of each shift-trellis row will be further braced by the addition of wooden tie-back posts driven into the ground at an angle and used to tie the end posts into position, preventing them from sagging in towards the center of the row. We will also create a wooden framework at the end of each shift-trellis row to further support the swinging trellis arm – this will be accomplished by driving another post into the ground 5 feet from each end post, securing it to the end post with a board across the top and 3/16” cable cross bracing across the bottom, and then screwing heavy-duty eyehooks into the top corner and bottom corner of this structure. This will create an additional place to secure the swinging trellis in both the horizontal and vertical configurations. Although this is another departure from Stiles (1999) LARS plan, we are unsure whether we can drive all of our posts the recommended four feet into the ground on our rocky hillside, and we want to ensure the stability of our trellis regardless.

    Conventional trellises (in the two control ‘Kiowa’ rows and the ‘Prime Jan’ row) will be constructed using T-shaped metal posts already available on the farm (we use them in several other trellising operations) and 12 ½ gauge fencing wire. They consist simply of driving a T-shaped post into the ground every 25 feet and then stringing high-tensile wire along the outside of the crossbar, forcing the canes to stay inside of the wire.

    Following Stiles’ (1995) instructions, trellis shifting will take place only after flowers have opened in all of the primary blosssoms of the current season’s floricanes. Demchak (2009) refers to this point as being two weeks post flowering.

    Any treatments for pests or fungal diseases will also have to be applied to the entire experiment, although we rarely need to apply products to our current bramble plantings. We have occasionally applied Oxidate, a hydrogen-peroxide based antifungal agent, to especially damp raspberry plantings that seemed highly susceptible to Botrytis mold; if that were to occur again, we would have to be sure to apply it to all four plantings even if some of the trellis systems seemed to be much drier than others. The only other pest control measure we have taken recently with brambles has been using Japanese beetle pheromone traps, which were last used here in 2008 to control beetle outbreaks. Due to our own doubts about their efficacy, we have not used them since, but if we did decide to use them again we would have to ensure that they affected all plantings equally – which should not be a problem as they would be placed several hundred yards away.

    Once harvesting begins, workers will record total and first-quality yields from each row, as well as harvesting time. In order to reduce the variation associated with worker efficiency, the same work crew will have to harvest every row, in sequence, rather than each person being assigned an individual row. For example, two workers may have to start on opposite ends of each row and work until they meet one another in the middle.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.