Extension of Local Food Production in Idaho Using High Tunnel Technology

Final Report for OW13-043

Project Type: Professional + Producer
Funds awarded in 2013: $49,999.00
Projected End Date: 12/31/2016
Region: Western
State: Idaho
Principal Investigator:
Dr. Stephen Love
University of Idaho
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Project Information


This WSARE High Tunnel project was conducted by 6 members of the Horticulture Team at the University of Idaho, Stephen Love, Jennifer Jensen, Tony McCammon, Ariel Agenbroad, Wayne Jones, and Stuart Parkinson. UI faculty are partnering with experienced high tunnel growers at GreenTree Naturals (Sandpoint, Idaho), Next Generation Organics (Homedale, Idaho) and Onsen Farms (Buhl, Idaho) to complete research and educational activities. The growers represent three regions of Idaho, northern, southwestern, and south-central. The project is comprised of three components: 1) research on high tunnel design with the objective to improve structural integrity under conditions of high winds and snow loads, 2) research to identify profitable crops and crop cultivars for use in Idaho high tunnel production, and 3) education on local food production using high tunnels through field days and publications.

Component 1: Design and construction of an experimental high tunnel was completed at Onsen Gardens in the spring of 2015. Design constraints included an aerodynamic shape and more closely spaced girders in the roof. Constructed side-by-side with a standard high tunnel, observations were completed to evaluate the performance and sturdiness of the new design. Evaluations included visual inspections to detect storm damage and the use of vibration detectors to measure structural stability. 

Component 2: Research to identify appropriate crops and cultivars for profitable high tunnel production was completed at the three cooperator sites. At Green Tree Naturals, evaluation of bean, eggplant, and cucumber cultivars were completed over three seasons. In addition to winter production of traditional salad crops, evaluation of high-value medicinal and homeopathic plant species was conducted at Onsen Gardens. Production of late-maturing, specialty pepper cultivars was conducted at Next Generation Organics. Cooperators assisted in accumulating crop value and monetary return data.

Component 3: Educational activities associated with the project included field days conducted within each of the three years of the project. Two field days and a workshop were held at Greentree Naturals in northern Idaho. Two field days were held at Next Generation Organics in southwest Idaho. Four field days, including two in 2016, were held at Onsen Farms in south-central Idaho. Educational videos and bulletins are currently being prepared as a culmination of outreach activities for the project.


The University of Idaho high tunnel project was developed at the specific request of small food producers in southern Idaho. Beginning in 2010, a coalition of research and extension faculty and Idaho food producers initiated a collaboration to augment local food production. The ultimate goal was to achieve a level of 20% locally produce foods in Idaho’s by the year 2020. A survey of local vendors revealed that the single major roadblock to accomplishing this goal is the lack of produce availability imposed by the short growing-seasons typical of Idaho’s climates (Cruz and Salant, in review). Grower’s and buyers communicated that season extension is paramount to enhancing local food production in Idaho. This high tunnel project was intended to increase the capacity for local food production in Idaho by providing research and outreach on the topic of more effective and site-appropriate high tunnel season extension technologies and production methods.

Recent work at other institutions has been conducted on topics associated with high tunnel food production, more specifically in Utah and Vermont. This proposal outlines work that is unique in three ways: 1) one of the major objectives of this project is to create and evaluation superior high tunnel designs, research that will benefit producers in all areas of US, 2) the project will be directed at foods deemed of value by existing buyers in Idaho and will evaluate crops and varieties unique to the market situation, and 3) Idaho has a unique range of climate conditions under which high tunnel technology must be evaluated (generally colder, shorter growing seasons, different annual % sunshine, and/or higher average wind speeds than locales previously evaluated.

In response to producer wishes, this project was designed specifically to increase grower knowledge and skills needed to effectively use high-tunnels. The project was developed using a logic model with defined inputs, outputs, and impacts.


Project Objectives:

Component 1, High Tunnel Design:

Objective: Improve high tunnel design to withstand high winds and/or high snow loads. Specific structural issues to be addressed include: methods to strengthen end-walls (the most common point of wind-related failure); alternate structural materials to replace PVC hoops (prone to snow-load failure); and improvements in covering materials to improve structure life and reduce weather-related degradation.

 Year 1

Review existing structural research on high tunnels relevant to high winds and high snow loads. (Completed)

Collaborate with producers, University of Idaho College of Engineering faculty advisor and senior engineering students to develop design recommendations. (Completed)

Collaborate with senior engineering students to test materials and conduct bench-scale research on structural options. (Completed)

Collaborate with senior engineering students to design and build demonstration research high tunnels and perform initial structural evaluations. (Completed)

Years 2 and 3

Evaluate performance of the improved structural high tunnel design (In progress)


Component 2, Crop Performance Research:

Objective: To identify crops and cultivars amenable to production in high tunnels and to extend the growing season for currently grown, high-value crops through the use of high tunnel technologies.

Year 1

Review existing research on high tunnel use with targeted crops suitable for Idaho. (Completed)

Collaborate with producers to organize crop trials and establish criteria for data collection. (Completed)

Year 2

Continuation of crop trials and data collection. (Completed)

Year 3

Complete crop trials and summarize data. (Completed)


Component 3, Education:

Objective: Provide research-based information to existing and prospective local food producers to encourage adoption of economically practical high tunnel production practices.

Year 1

Provide producer/professional education through field day/tours. (Completed)

Year 2

Present field day/tours and distribute educational materials. (Completed)

Year 3

Present training workshops statewide based on trial results and best practices. (Planning Stage)

Develop a DVD and written educational materials for distribution to producers and agricultural professionals. (Footage shot for the video, publications in the writing phase)

Produce two professional publications for refereed journals detailing the methods and results of the project. (In the planning phase)


Click linked name(s) to expand/collapse or show everyone's info
  • Ariel Agenbroad
  • Michael Bauer
  • Stanley Carpenter
  • Lance Ellis
  • Chris Florence
  • Diane Green
  • Jennifer Jensen
  • Wayne Jones
  • Tony McCammon
  • Chance Morgan
  • Geoff Neyman
  • Stuart Parkinson
  • James Reed
  • Leslee Reed
  • Susan Wesendorf


Materials and methods:

Component 2:  Improve high tunnel design to withstand high winds and/or high snow loads. Specific structural issues to be addressed include: methods to strengthen end-walls (the most common point of wind-related failure); alternate structural materials to replace PVC hoops (prone to snow-load failure); and improvements in covering materials to improve structure life and reduce weather-related degradation.


Year 1

  1. Review existing structural research on high tunnels relevant to high winds and high snow loads.
  2. Collaborate with producers, University of Idaho College of Engineering faculty advisor and senior engineering students to develop design recommendations.
  3. Collaborate with senior engineering students to test materials and conduct bench-scale research on structural options.
  4. Build a full scale on-farm structure and compare performance to a standard high tunnel.

Year 2

  1. Evaluate performance of the new design under heavy wind and snow stress load conditions.
  2. Integrate design and structural information into workshops, tours and educational materials.

Year 3

  1. Complete structural performance evaluations.
  2. Integrate design and structural information into workshops, tours and educational materials.


Component 2:  To identify crops and cultivars amenable to production in high tunnels and to extend the growing season for currently grown, high-value crops through the use of high tunnel technologies.

Year 1

  1. Review existing research on high tunnel use with targeted crops suitable for Idaho.
  2. Collaborate with producers to set up crop trials and collect data. Include specialty and medicinal crops.
  3. Provide producer/professional education on crop topics through field day/tours.

Year 2

  1. Expand crop trials and data collection activities.
  2. Present field day/tours and distribute educational materials.

Year 3

  1. Complete crop trials and summarize data.
  2. Present training workshops statewide based on trial results and best practices.
  3. Develop DVD and other educational materials for distribution to producers and agricultural professionals.
  4. Present final field day/demonstration tours and distribute educational materials



Research results and discussion:


The University of Idaho team responsible for this project consisted of six faculty members. The team worked with three grower/cooperators. Growers were experienced high tunnel, organic producers and represented the range of climatic conditions across the state of Idaho.  The northern site was in Sandpoint, Idaho; grower Diane Green, Greentree Naturals.  The southwestern site was in Homedale, Idaho: grower Bart Raynes, Next Generation Organics. The south-central site was in Buhl, Idaho; grower James Reed, Onsen Farms.

To enhance the project, one new high tunnel was constructed on the property of GreenTree Naturals and two high tunnels at Onsen Farms. Crop trials began in the summer of 2014 and extended through the fall/winter of 2016/2017.  The extension educators on the team worked with the farmers to collect data related to tunnel structural and environmental performance and crop and cultivar economic potential.

Multiple field tours were conducted at each site over the life of the project. Outreach was geared toward other small acreage farmers.

CASE STUDY: Greentree Naturals – Sandpoint, Idaho

 Jennifer Jensen, Bonner County Extension Educator, coordinated Northern Idaho component of the project.

Diane Green and Thom Sadoski have been running Greentree Naturals as a certified organic farm since 1992. Greentree Naturals Farm is located 12 miles northeast of Sandpoint.  The cultivated area on the farm is approximately 2.5 acres, but continues to grow. After starting out selling excess produce at a farmer’s market in 1990, they slowly expanded to include selling to restaurants, a CSA subscription service and on-farm research and educational events (DePhelps, et al 2005).  Diane Green sells organic vegetables, herbs and flowers. 

Greentree Naturals Farm has utilized smaller sized hoop houses (approximately 13’ wide with varying lengths) for crops such as cucumbers, peppers, and tomatoes. Although these would technically fit the description of a high tunnel (Blomgren and Frisch, 2007), a larger sized high tunnel was installed for this project. This structure will hence forth be referred as the high tunnel. The high tunnel is 24’ x 48’ and is a gable style from Northwest Garden Domes.

At Greentree Naturals Farm we wanted to record seasonal temperatures from the larger high tunnel, one of the smaller hoop houses, and from the unprotected outside. A Hobo temperature sensor was located in each location on a stake about 1.5 feet high to measure the air temperatures around the plants. These sensors were set to record the temperature every half hour. From this, you can see the high and low temperatures in each location in the following figure for 3 years of the project. The sensor was not installed until July 30, 2014 the first year of the project. In 2016, a problem caused the sensor in the hoop house to stop recording temperatures after August 20, 2016.

Daytime temperatures were highest in the hoop house, followed by the high tunnel, and then the unprotected outside. Temperatures in the high tunnel and hoop house were in the range of 5 to 10 degrees warmer that outside. One some days, the temperatures outside were more than twenty degrees cooler than in the hoop house and more than fifteen degrees cooler than in the high tunnel. Night-time temperatures were much more similar in the three environments. The high tunnel and hoop house, for all intents, exhibited the same temperatures and were one to two degrees warmer that outside.

The high tunnel is used to grow cucumbers, eggplant, basil, peppers. For this presentation we will be focusing on the high tunnel cucumbers compared to the hoop house cucumbers and the high tunnel eggplant compared to eggplant grown outside. It is noted that the eggplant grown outside is grown with a black plastic mulch to help retain heat. The cucumber cultivar is ‘Green Fingers’ and the eggplant cultivar is ‘Travaita’.

Eggplant ‘Traviata’ was evaluated inside and outside the high tunnel. ‘Traviata’ is a high yielding, traditional bell shaped eggplant. This cultivar showed the highest yields in the the trials conducted by the Agricultural Experiment Station of the University of Rhode Island in 2013.  The eggplant both inside and outside was grown with a black plastic mulch.  Both had drip irrigation. According to some seed catalogs, ‘Traviata’ is suited to both greenhouse and field production. The eggplant grown outside averaged only 51% of yields inside the high tunnel. In 2016, the outside crop was a complete failure while the high tunnel crop was exceptionally high.

Cucumber ‘Green Finger’ was the cultivar used in this project to compare performance of the high tunnel with the hoop house. The results were not consistent and varied by year. In 2014 the plants in the hoop house yielded greater number of cucumbers than the plants in the high tunnel.  Reversely, in 2016, the plants in the high tunnel yielded greater numbers of cucumbers.

In addition to the amount of yield, we also recorded gross profits.  Greentree Naturals was able to market all products either through retail markets or through wholesale markets. Eggplants included in the study grown outside averaged $86.16 in profits. When grown in the high tunnel, they brought in $226.23. Cucumbers in the hoop houses averaged $141.58, while those produced in the high tunnel averaged 194.75, in spite of the hoop house outperforming the high tunnel two out of the three years.

The first year a field day tour was scheduled towards the end of the growing season to demonstrate how the high tunnel and the hoop houses were being used to extend the growing season. Information gathered from the first season was shared with the group.

The second year another field day was conducted to showcase the project and demonstrate using the high tunnel structures for season extension. This field day was not as well attended as the previous year, but it may have been influenced by the cold wet weather on the day of the tour. 

The third year another field day tour was scheduled near the end of the season, but was cancelled due to lack of interest. Instead, a workshop was held in November of 2016 to discuss the full three years of the project. This workshop was held at the extension office so it did not include a tour. However, many pictures were presented in power point presentations.

 Conclusions: This study on Greentree Naturals Farm showed that high tunnels or other structures can have an impact on production of vegetables. It was not the intent of this farm to extend the growing season beyond the frost dates, but rather improve production during the normal growing season.  The eggplant grew particularly well in the high tunnel, especially in 2016. From the farmer, Diane Green, “The eggplant, hands down thrive and produced exceptionally better in high tunnel than outside in black plastic.” 

The results from the cucumber experiment were mixed.  A closer look at the economics of the production might help determine if one structure is more profitable that another. The small hoop house structure is relatively inexpensive even compared to a high tunnel. Greentree Naturals estimates that they spent about $600-$700 to construct the 13’ x 36’ hoop house while the high tunnel cost approximately $3,300 (not counting labor).

Further research on crop production and the economics of high tunnels should help farmers determine if they are right for their farms in Idaho. It does seem clear though that a farmer should be able to produce greater yields, thus increasing the amount of locally produced food available, by having high tunnels.


CASE STUDY: Next Generation Organics – Homedale, Idaho

 In Southwest Idaho, Extension Educator Ariel Agenbroad collaborated with certified organic grower Bart Raynes of Next Generation Organics. Bart grows on a small acreage in Homeldale, Idaho, in Owyhee County. Next Generation Organics specialize in early spring certified organic plant starts, specialty fruits and vegetables and hand ground, minimally processed polenta corn. These products are marketed at the Boise Farmers Market (outdoors April – October and indoors November and December), the Boise Food Coop, and the small Cliff’s Market in Caldwell, Idaho.

Bart was approached to participate in this project because of his innovative approach to farming, his curiosity and willingness to try new things, and his commitment to open sharing of knowledge.

Bart has two high tunnels, one is fixed, one is moveable. Bart is an experienced grower, with well designed, resilient high tunnels. His interest in the project was primarily financial. Which crops/crop rotations would be most profitable in the high tunnel? Over three years of the project we explored three different scenarios with that goal in mind.

The first year of the project, Bart explored fall cropping systems in the moveable high tunnel. He was interested in garlic, shallots, and specialty winter salad greens like forced endive, a crop restaurants and winter Farmers’ Market customers were requesting. He initially looked at postponing the fall planting of crops in the high tunnel while getting later harvests from summer field crops. For example, he planted garlic in the moveable high tunnel in late November, early December (instead of the usual September in this area) and found that it satisfactorily caught up to or exceeded traditional plantings by the time the high tunnel was moved to a new location. While this was a good use of the high tunnel, the profitability of one garlic crop was not high enough to dedicate high tunnel space to it every year, and the specialty winter greens, like forced endive, proved too labor intensive to be economically feasible on a small scale.

In year two Bart continued exploring using his high tunnels to increase production and speed the ripening of high value direct and retail specialty hot and sweet peppers. Despite high temperatures and a long growing season, peppers performed below expectations in 2016. While in general, the peppers grown in the high tunnel grew more vigorously, yielded earlier, and ripened sooner than the same cultivars grown in field, the differences were not significant across all cultivars. However, a few specific cultivars showed a marked increase in yield and several weeks advance ripening versus the same cultivars in field. ‘Ancho’ was one pepper that performed in this way. Some of the peppers of interest to local specialty markets, such as the infamous ‘Ghost’ pepper, were slow to yield and ripen whether in or out of protection.

Prolonging the harvest of the specialty peppers with the use of the high tunnel did permit Raynes to have these items through October and into early November, despite a killing frost in October. The plants inside the unheated high tunnel persisted until November, providing product for an additional 3-4 weeks. The Boise Farmers’ Market operates until mid-December, so having these crops longer was beneficial.

Originally, Raynes used the high tunnels on his farm primarily for market tomato production. Throughout this project, Raynes investigated direct- and retail-marketed nontraditional specialty crops that could be overwintered (garlic, specialty greens), ripened earlier and harvested longer (specialty hot peppers) in his high tunnels. While the high tunnels offered some increase in production, yield, and marketable season for these crops, Raynes now feels confident that tomatoes are in fact the most profitable crop that he grows in his Next Generation Organics operation, and that high tunnel production of tomatoes is the most economically viable. Over the past three seasons, Raynes has seen significant field crop losses of tomatoes due to viral and bacterial diseases that are widespread throughout the growing region. These diseases, especially the Curly Top Virus, have not been problems in his high tunnel-grown tomatoes.

For the 2017 season, Raynes is exploring growing grafted tomato plants in the high tunnel for their purported additional vigor and disease resistance. He purchased grafted tomatoes and began the process of growing and grafting his own seedlings, with success. He is also exploring additional use of low tunnels and “quick hoops” for use in the field throughout the growing season.

The 2016/2017 winter proved disastrous for some growers using the Quonset or traditional hoop high tunnels. A local farm experienced almost a 50% loss of structures due to exceptional snow loads. Raynes’s gable/gothic style high tunnels were undamaged by the storms. He has also developed a very simple, handmade high tunnel “snow rake” for removing snow from his 13 foot tall houses.

In September 2015, Bart hosted a field day for the University of Idaho Extension Small Farms team. Participants were introduced to the moveable high tunnel, observed the garlic and greens, and explored additional ways in which the Raynes were using their high tunnels for maturing and ripening of storage crops, production of ornamental succulent plants, and fall cropping. We did not host a field day at Next Generation Organics this year but will be using Rayne’s contributions in upcoming presentations, publications and resources in order to share his findings with other growers.

Conclusions: In southwest Idaho, greater production and season extension were made possible by use of high tunnels in vegetable production. For crops such as garlic and peppers, the production advantage did entirely make up the extra cost of high tunnel production. Tomatoes grown in high tunnels were markedly more profitable than those field-grown.


CASE STUDY: Onsen Farms – Buhl, Idaho

 Under the guidance of Tony McCammon, area horticulture educator for the Twin Falls region, distinctive high tunnel work was completed at Onsen Farms in Buhl, Idaho.

Onsen Farms is a small, organic production facility. They take advantage of unique geological features that provide unlimited supplies of both hot and cold water from free-flowing artesian springs. This allows them to profitably grow winter crops that are typically difficult to produce where supplemental heating is required. Most of the Onsen Farms production has historically been in the winter months when supply is limited and prices are high. They sell high-value vegetables into CSAs and farmer’s markets. James Reed, the owner of Onsen Farms has been instrumental in building coops across southern Idaho in order to reduce transportation costs and increase profits for the network of small organic growers that live in the area.

 Within the scope of the University of Idaho high tunnel project, Onsen Farms was a key site for both research and education. Two new high tunnels were constructed on the farm. One was a standard, kit-manufactured structure. The other was designed by a team of University of Idaho senior engineering students specifically to withstand heavy snow loads and high winds, destructive elements that frequently destroy high tunnels in Idaho. The experimental tunnel was designed with a stream-lined upwind wall and closely-spaced roof supports. The two tunnels were constructed side by side and performance carefully observed.

Ideally, a weather event destructive to the standard high tunnel would have validated the new design. However, both tunnels withstood environmental conditions experienced during the time span of the study. As an alternative measure of design effectiveness, we provided vibration-detection instrumentation for the measurement of vibration and motion during wind events. Study results are still being analyzed, but preliminary results show less vibration and increased wind tolerance in the tunnel with the engineered end wall. The design specifications of the improved high tunnel will be published and made available to growers.  

Crop production values, although not measured experimentally, were tallied for the two new high tunnels. James Reed and his staff recorded the crops grown and profit/loss of production during the three years of the project.

Winter 2014-2015: This was a low-profit year for crops produced in the new high tunnels. Consistent crop failure occurred “due to overly-excited gardeners” who made heavy applications of raw compost. Crops raised included braising greens, tomatoes and a few short crops of lettuce and spinach. Estimated value: $400.

Winter 2016-2016: Growers reported that soil was still maturing and not yet fully productive. Crops raised included spinach, lettuce, braising greens, tomatoes, cucumbers, parsley, arugula, and endive. Estimated value: $3,500.

Winter 2016-2017:

Growers reported a bumper crop of kale, lettuce, spinach, tomatoes, potato fingerlings, herbs, cauliflower, and many different types of micro-greens.  They sold the crops through CSA’s and contracts with local restaurants and locally grown produce markets. Estimated value: $6,000.

Onsen Farms was the site of some preliminary testing of unique crop species. Perennial medicinal plants that have high value but not adapted to Idaho growing conditions were planted, in the high tunnels and monitored for growth and survival. Crops we studied included patchouli, helichrysum, oregano, melaleuca, rosemary, thyme, spearmint, persimmon, and ginger. Only patchouli did not germinate and grow well in the high tunnels. The other species survived the winters and were productive.

As a result of this component of research, Onsen Farms has initiated a new branch of business, medicinal plant production. They have started selling the plants ate farmer’s markets and through CSAs along instructions on making tea’s and tinctures.  

Each of the three years of the project, field days were conducted at Onsen Farms. The field days were very well attended and we had participation of local news media. We finished up the project in 2017 by offering two field tours at Onsen Winter gardens; one in March and again in January of 2017.  We averaged 30 participants in each field day and the results of the research project. Thirty-nine survey sheets were collected illustrating that 100% of participants indicated a willingness to change behaviors as a result of what they learned at the field day.  Nine-two percent recorded improved knowledge and awareness of ideas or skills participants planned on not only using but sharing with others as well.

Conclusions: Early evidence suggests a specially-designed high tunnel with aerodynamic shape and greater density of girders is more wind and snowload resistant than similar standard kit designs. The new design may benefit growers where these environmental issues are a problem. Crop evaluations demonstrated that high tunnels can be used to produce high-value medicinal crops that are otherwise not adapted to southern Idaho climates.

Participation Summary

Research Outcomes

No research outcomes

Education and Outreach

Participation Summary:

Education and outreach methods and analyses:

As a result of this project, the Horticulture Team has initiated authorship of the following educational products:

1 professional oral presentation that can be used for professional or farmer education.

2 farmer-friendly publications; one describing the specifications of an improved high tunnel design; one describing the results of crop/cultivar studies.

2 refereed journal articles describing the details and impact of the study and also the results of crop studies.

One video demonstrating the construction of a high tunnel, specifically with improved design characteristics.

Education and Outreach Outcomes

Recommendations for education and outreach:

Areas needing additional study

Topics growers expressed a need for:

Additional information on crops and cultivars that are amenable to high tunnel production.

Methods for meeting nutritional needs of plants in high tunnel culture.

Economical practices for building and maintaining high tunnels.

Any activities that will increase exposure and improve knowledge of local food production systems in the general public. The ultimate goal being to increase the potential market place.

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.