Evaluation of High Tunnel Systems for Spring Organic Lettuce Production in Georgia

Project Overview

Project Type: Graduate Student
Funds awarded in 2015: $11,000.00
Projected End Date: 08/31/2017
Grant Recipient: University of Georgia
Region: Southern
State: Georgia
Graduate Student:
Major Professor:
Dr. Suzanne O'Connell
University of Georgia

Annual Reports

Information Products


  • Vegetables: greens (lettuces)


  • Crop Production: cropping systems, high tunnels or hoop houses, organic fertilizers, row covers (for season extension)
  • Farm Business Management: farmers' markets/farm stands, market study
  • Pest Management: cultural control, prevention, weather monitoring
  • Production Systems: organic agriculture, organic certification
  • Sustainable Communities: local and regional food systems, urban agriculture



    The goal of this project was to investigate organic spring lettuce production under high tunnels compared to the open field in Georgia. We evaluated the effect of high tunnels, three planting dates and 12 cultivars (i.e., 6 butterhead and 6 romaine lettuce types) on lettuce yield. A greater marketable fresh weight for both butterhead and romaine lettuce was observed under high tunnels compared to the field in 2016 but not in 2015, indicating the advantage may depend on yearly weather conditions. The butterhead cultivar “Sylvesta” and the romaine cultivar “Green Forest” consistently performed well in both the high tunnels and field.

    High tunnel lettuce was harvested 2 to 7 days earlier than the field depending on the year. The added protection from the high tunnel system plus row covers prevented the air temperature dropping below 32oF on freezing nights (i.e., 6-9°F greater in high tunnels) while maintaining approximately 1-2°F greater average daily air temperature compared to the field system, across the entire growing season. Other micro-environmental differences between two production systems included decreased leaf wetness and decreased photosynthetically active radiation under the high tunnel systems. Pests, diseases (e.g., Sclerotinia sclerotiorum) and physiological disorders were not different between the two systems.

    In addition to the field study, a consumer survey was conducted to identify the lettuce preferences by shoppers at the Athens, GA farmers market. Participants answered questions about purchasing habits, visual appearance and rated the taste of four butterhead and/or romaine cultivars. The cultivars chosen represented those that performed the best under the high tunnels or had unique visual appeal. The majority of the participants ranked ‘freshness’, ‘taste’ and ‘visual appearance’ as the top three attributes affecting their lettuce purchases. Among the four butterhead cultivars, ‘Sylvesta’ received the top ranking while all four romaine cultivars evaluated, ‘Green Forest’, ‘Salvius’, ‘Super Jericho’ and ‘Red Rosie’ ranked similarly.


    The goal of this project was to investigate organic spring lettuce production under high tunnels compared to the open field in Georgia. Many farmers are interested in capturing the local lettuce market and view high tunnel systems as a tool to achieve this goal. High tunnels can protect crops from extreme weather events (i.e., precipitation,  frost, wind, cold) and result in better overall crop quality and earlier yields and is therefore is attractive (grower communication). NRCS high tunnel cost share programs have made this an even more attractive idea to explore. Between 2010 and 2014, NRCS awarded more than 480 awards to Georgia farmers for high tunnel construction.

                The majority of current high tunnel literature is based in Northeast and North Central regions where the production challenges are different than the Southern region. There is a lack of recommendations for the Southern region even with the growing popularity of these systems. Rapidly fluctuating temperatures and a quick transition from spring to summer are typical challenges for high tunnel lettuce production in the South. Lettuce is a cool season crop with optimum day-time and night-time temperatures of 73°F and 45°F, respectively (Jackson et al., 1996); higher temperatures often result in physiological disorders including bolting (i.e., flowering), bitterness, tip-burn, and poor heading (Rader and Karlsson, 2006).

                 Many high tunnel studies have found increases in crop yield and quality (O’Connell et al., 2012; Rader and Karlsson, 2006; Waterer, 2003) but location, timing and crop selection are all factors to consider. Based on previous studies it appears the high tunnel environment can present unique challenges for lettuce production and may require a separate set of management practices including variety selection to perform optimally. Therefore, our study evaluates the performance of six butterhead and six romaine lettuce varieties in high tunnels compared to the field at three different spring planting dates. The varieties were chosen based on grower or seed company recommendations. Growing systems will be compared for effects on crop yield and quality and microclimate will be characterized for each system. Lastly, we conducted a consumer taste test and visual assessment of the top-performing varieties to better understand local market preferences.

    Project objectives:

    1) Evaluate the effect of high tunnels on spring organic lettuce production in Georgia.

    2) Compare the performance of different lettuce varieties in each growing system.

    3) Assess the effect of three different planting dates on crop yield. 

    4) Describe the microclimate of each growing system throughout the spring season. 

    5) Conduct consumer taste test and visual assessment of the top-performing lettuce varieties to better understand market preferences.

    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.