Can Shade Cloth and Mulch Extend the Greens Season in the Midwest Region?

Final Report for FNC01-374

Project Type: Farmer/Rancher
Funds awarded in 2001: $5,000.00
Projected End Date: 12/31/2006
Grant Recipient: Cultivate Kansas City
Region: North Central
State: Kansas
Project Coordinator:
Katherine Kelly
Two Birds Farm
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Project Information



In the summer of 2002, Full Circle Farm was a certified organic vegetable and herb farm in its sixth year of operation on 2 acres in Kansas City, Kansas. We specialized in interesting varieties of herbs, lettuces and salad greens. Since then the farm and business have continued to evolve, expanding the range of organic produces grown to include fruit, and increasingly, tomatoes, in season. In late 2004 we changed the farm’s name to the Kansas City Community Farm, when we established the non-profit Kansas City Center for Urban Agriculture. The Kansas City Community farm operates as working, certified organic vegetable farm to develop and demonstrate production practices suitable for Midwestern urban agriculture.

Other project partners were Robbins and Jim Hail of Bear Creek Farm, Osceola, Missouri, which operates a certified organic vegetable farm, and makes extensive use of hoop houses for season extension and crop protection. Also, Ted Carey, vegetable specialist at K –State Horticulture Research and Extension Center, Olathe, Kansas was establishing organic vegetable production research plots and season extension research and demonstration using high tunnels at the time this project was conducted.


Original Project Description:

Most varieties of green do not grow throughout the market season in the Midwest because of the 85-degree-plus weather, which persists for much of July, August, and September. The ability to extend the greens season through the summer heat would benefit local producers while meeting a consumer need at peak market times. Fresh lettuces, arugula, and increasingly, specialty green, are crops that provide significant income for growers in the spring and fall. The increased income potential for small organic growers and diversification of summer vegetables would help sustain the local organic community. Consumers seeking fresh, local, organic green for taste, health and environmental reasons would benefit from a long prolonged greens season.

The overall goal of the project is to develop a set of practices that will permit the production of lettuce and other cooler-climate-requiring green leafy vegetables throughout the mid-western summer season. Specifically, we will evaluate lettuce cultivators and other selected green leafy vegetables to assess their heat tolerance and production potential in the Kansas City area. We will also investigate the potential of selected shade cloth, mulch, and row cover combinations to reduce soil and air temperatures and control pests. The project will take place over two years, with the second year further developing and refining procedures from the last year.

Objective One: Test 17 varieties of lettuce and six varieties of mustard greens to determine what varieties and types of green produce the best under hot summer conditions when shade cloth is used.

Objective Two: Test combinations of white shade cloth, mulch, and floating row covers to reduce soil and air temperatures and to control pests.

Objective Three: Determine if the capital investment and extra labor involved in growing shade cloth is justified by the income potential.

Objective Four: To develop a documented, workable, and affordable system for growing greens in the Midwestern summer heat than can be used by other growers.


Original Process

We would use the SARE grant to determine whether the greens season can be extended in to the hot summer months using the following system: 1 test plot of green under 28% white shade cloth and a control plot without shade cloth. Each plot will consist of one 4’x150’ bed for a total of 1200 square foot in green production at each of the three sites. One third of each planting will be covered with white plastic mulch, 1/3 will be covered with straw mulch, the last third will be uncovered. Each bed of green will have a drip irrigation buried 2-3” below the soil surface. The shade cloth will be suspended on 7” t-posts (approximately 6’ above the ground) using cable and t-post insulators. One side of the horizontal (top) panel will be rigged with s-hooks so the panel can be pulled back for rain and cloudy days. Similar shade structures will be set up in mid-May; the first transplants will be started in mid-May and set out in early June. New plantings will be done every three weeks after that.

Actual Process

This was the second year of the project. By beginning of the second year, based on first year results, we changed the green production system in the following ways.

Shade Cloth Suspension: After talking with other producers and extension specialists, we decided that a high-tunnel structure would be less intensive and more productive than simple shade cloth suspended directly over the field. We constructed 18’x30’ high-tunnel at all three sites. The tunnels were covered in 6 mil plastic and then covered with 39% white shade cloth.

Straw and Plastic Mulch: In the first year, we found that straw mulch made the high tunnel too hot because it reflected the sun back up and overheated the greens, the lettuces, and the workers. It was also too cumbersome and was unpleasant to work with in the summer heat. We also decided not to try the white plastic mulch, because in Year One we grew transplants for head lettuce production and in Year Two we switched to direct seeding for baby-greens salad ingredients. We didn’t know of a system for direct seeding into plastic mulch, so we simply direct seeded into bare soil.

Drip Irrigation: With direct seeding, we found that drip irrigation is inefficient in keeping the seeded areas damp and cool enough for good germination. (If the drip tape is not directly on top of the seeds, too narrow a band of soil in moistened and cooled and too many of the seeds don’t germinate.) In the second year, we started direct seeding in the afternoon and then using overhead misting/sprinkling to cool the soil, provide the seeds with a good damp seedbed, and take advantage of cooler nighttime temperatures. We watered this way daily until germination. We direct seeded lettuce varieties and Asian green varieties at each site, using overhead misting/sprinkling. All were harvested at baby size for salad mixes.


Katherine Kelly, Full Circle Farm, Ted Carey, K-State Research and Extension, Robbins and Jim Hail of Bear Creek Farms


Since this was a two year project supported by Organic Farming Research Foundation (first year) and SARE second year) we present results from two years of trials here. Summary results of 2001 trials are presented in Table 1, and indicate consistently higher yields of lettuce and leafy green crops grown in high tunnels than in open field plots. This translated into a higher value of lettuce and leafy green grown in shaded high tunnels than open field plots. Results of 2002 trials are presented in Figures 1, 2, and 3, and present yields from multiple plantings of lettuce and leafy greens at each location. At Bear Creek Farm (Figure 1), three plantings were actually made during the season but outside plots of the second and third plantings failed to establish and this produced no yield. At the K-State site (Figure 2), yield trends in shaded high tunnels were relatively consistently superior to open field plots. At Full Circle Farm (Figure 3), yields from shaded high tunnels were generally superior to those in open field plots during the first and second trials. However, data indicated markedly higher yields from open field plots in trials three and four. This does not coincide with our recollection of the trial results, so it is possible that a systemic error occurred during data collection, leading to a mix-up of inside and outside results.

The advantages of growing lettuce and leafy greens in shaded high tunnels as compared to the open field were almost immediately obvious to the cooperators at each location.
Shade-grown lettuce and greens grew larger, faster than their open-field-grown counterparts, and appeared to have consistently higher quality, being consistently cleaner (due to lack of rain splashing) and more succulent. In year 1, total yields from inside shaded high tunnels were consistently higher than from outside. At Full Circle Farm, the retail value of the harvest from the high tunnel was greater than the cost of materials to construct the high tunnel. At Bear Creek Farm and the K-State Research and Extension Center, the value of harvest came close to matching the cost of the tunnels. As these structures have an anticipated life expectancy of several years, it is remarkable that in a single season they come close to paying for themselves.

Table 1. Total lettuce and green planted and harvested, total harvest weight and value by farm, planting date and whether planted in shaded high tunnels or open field. Trials conducted during the summer of 2001.

We also sampled the varieties for taste and bitterness over the season and asked customers for feedback as well, and found that there was no perception of summer bitterness or toughness.

During 2002, we gathered daily soil and air temperature data from inside the shaded high tunnels and adjacent outside plots during the course of the experiment. Figures 4, 5, and 6 present daily graphs of air and soil temperatures at Bear Creek Farm during 3-day periods in early June, July, and August. Air temperature highs were either slightly higher inside tunnels than outside (early June), or very similar. Air temperature lows were consistently slightly higher in the tunnels than in the field, probably due to the insulating properties of the plastic tunnels. Soil temperature highs in tunnels were consistently lower than outside soil temperatures, and lows in tunnels were consistently lower than outside soil temperatures, and lows in tunnels were either lower than or similar to outside soil temperatures. Soil temperature highs in the high tunnels were similar to or lower than air temperatures in the tunnels, while soil temperature highs outside frequently exceeded air temperatures. Lower root temperature has been reported to be an important factor for favorable lettuce growth (Thompson et al,. 1998), and the consistently superior performance of lettuce and greens grown in our shaded high tunnels may be at least partially attributed to the cooler soil temperatures in our tunnels compared to adjacent field plots. It is likely that other factors, such as reduced wind, reduced light intensity and modified light quality (reduced ultraviolet) also contributed to the superior performance of shaded high tunnel-grown lettuce and greens compared to those grown in open fields.


In general, we found that it was impossible to grow baby greens and lettuce under shade cloth in the summer heat. We found that direct seeding was effective and that misting did improve germination, tenderness, taste and yields.

In the years since conducting this work, we also have found that all types of crops produced in the summer in the high tunnels (with shade cloth and without) are of better quality and yields than field produced crops. As a consequence, we found ourselves making choices between planting a high producing, high dollar, and high demand crop like tomatoes into the high tunnels versus planting lettuce/greens. All three sites have since dedicated the majority of our high tunnel space to higher-yielding, more profitable heat adapted crops like tomatoes and melons and cucumbers and set aside a small amount of space for greens production, primarily in response to customer interest in having some lettuce and greens available throughout the season.
We also found that, while the harvested green were beautiful when first harvested and brought to the farmers’ market, they did not hold up well in the summer heat radiating off the parking lot pavement, and that we lost too much of the product to wilt. Bagging, rather than our traditional bulk sales, helped with this issue some, but the green often wilted in the bag.

We would (and have) recommended to other growers that it is a system worth trying, but that we did not ultimately find it was the best use of high-value high tunnel and shade-cloth growing space and limited labor hours.


Original Outreach Description

The project will be digitally recorded and made available as a 20 minute VHS video showing the building of the experimental structure, the process of growing and harvesting greens, and our results. A written report will also be created.

Both will be made available through the Barstow Organic Farmers Market and will be used in 2003 as a centerpiece for presentations at the Great Plains Vegetable Growers Conference in January and at the Kansas Rural Center’s Small Farm Day in April. Distribution will be through the NOFA video program, seed catalogues, the Eastern Kansas OCIA chapter and our website.

Also, trials conducted at the K-State Research and Extension Center will have a high profile demonstration role. They would be used to explain and demonstrate to visitors during field days.

Actual Outreach Activities

In January of 2002, we presented a one-hour workshop on the results of the first year of the project at the Midwest Vegetable Growers Conference where we showed a video of photographs and live footage of the project to about 100 people. The information was well-received and was one of the early outreach activities promoting high tunnels and shade cloth for summer vegetable production. Farm tours to Full Circle Farm and the K-State Research Center also took place in 2002 and 2003 specifically looking at high tunnels and the summer greens trials.

A video of the project is being posted on and will be available upon request. Additionally, as an outcome of this project, Edward Carey has presented talks on the use of shaded high tunnels for season extension of cool season crops. Robbins and Jim Hail and Katherine Kelly, as leaders in high tunnel production in this region, also have talked individually and informally to a wide variety of growers about the project and its results. We learned that while this system “worked” it wasn’t necessarily one that we would recommend. Given this, we have not publicized the results as widely as we originally anticipated.


Participation Summary
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.