Shade cloth for fall bearing blackberry druplet abortion/malfunction problems in southeastern USA

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2013: $6,458.00
Projected End Date: 12/31/2016
Region: Southern
State: South Carolina
Principal Investigator:
Walker Miller
The Happy Berry Bunch

Annual Reports


  • Fruits: berries (brambles)


  • Crop Production: shade cloth


    The project tested hypothesizes of making a trellis made from locally sourced materials that enabled operation of tractors/ sprayers on steeply sloped hills of the inner Piedmont of the southeast as well as support shade cloth to provide cooler conditions for improved yield and quality of blackberries. The trellis did so successfully except for an unanticipated problem of reduced soil evaporation resulting in tractor sliding. The shade cloth failed to provide cooler conditions or the anticipated benefits. The reasons why and the outreach program are discussed.


    The problem was to provide a consumer desired, quality crop product to harvest, which is not available in the fall (September to December) market window, not be exposed to excessive price competition globally or otherwise, and would not be damaged by spring frost. To “thumbnail it” develop a new alternative crop for growers to become more economically, environmentally and socially sustainable. Recently developed fall bearing blackberries by Dr. John Clark at the University of Arkansas represents such an opportunity. The problem is that high summer temperatures in the southeast are causing reddening, white and abortion of drupelets and resulting in malformed berries with lower yields. Dr. Clark points out in his presentations and reports that beautiful fruit is produced in research trials in the cooler climate of the Pacific Northwest and California. In a personal communication he suggested that flowers formed when temperatures exceed 85 degrees Fahrenheit are smaller and malformed. Personal observation is that the frequency of white, dried, aborted drupelets is greater when exposed to direct sun. Therefore, the problem becomes to reduce the temperature and direct exposure to sunlight.

    While hosting an extension researcher from Israel he pointed out that 30% shade cloth was used to produce berries free of similar problems in spring and summer bearing berries in Israel. Since we are about 850 feet in elevation and perhaps cooler, we planted a very small test planting of Black Magic and Prime Ark, both fall bearing and both with relatively soft berries when compared to commercial variety like Navaho. The soft berry means a very short marketing time line, an ideal situation for direct marketing, and local food shed growers in the southeast. The 2012 season was a cool season with great blackberry growth but still we had reddening, white and abortion of drupelets and malformed berries associated with hot temperatures of summer. If you are to use shade cloth the problem becomes to create a shade cloth support structure/system in the field adaptable to uneven terrain, that uses locally available supplies, cost less than commercially available systems, provides for vegetation management and pest management, is retractable when temperatures are good for good flower formation for maximum photosynthesis, deployable when hot weather or freezes threaten. A potential side benefit would be freeze protection by reflecting heat back into the canopy instead radiating out during radiational freeze on windless, clear nights.

    The final part of the problem is to verify that proposed benefits of lower temperatures, better quality berries, and prevention of heat loss can be realized. Lastly, sustainability is achieved by reduced risk in producing high quality blackberries and increased reliability of cropping in the spring, cropping in a now empty market window and prolonged cropping in the fall over ambient conditions.

    Project objectives:

    Develop a trellis system for shade cloth deployment and retraction that would enable normal tractor operation for mowing, air assisted spraying and directed weed management sprays using locally available supplies. The second objective is to verify hypothesized impacts of lower summer temperatures improved quality berries, higher yields and reduced heat loss in frost events.

    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.