Extending the Vegetable Growing Season in Northern Michigan with Polyhouses

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 1996: $2,696.00
Projected End Date: 12/31/1996
Matching Non-Federal Funds: $2,314.00
Region: North Central
State: Michigan
Project Coordinator:


  • Vegetables: tomatoes


  • Natural Resources/Environment: biodiversity
  • Soil Management: composting


    There is high demand for fresh produce in northern Michigan markets, but local growers are essentially prohibited from exploiting this demand by a short growing season. This project could demonstrate methods that would allow area growers to service a local demand for quality produce, potentially increasing farm income. Early availability of local produce will also allow local farm markets to establish a stronger relationship with their customer base that could lead to an increase in return customer visits as the season progresses.

    To study the use of high-tunnel polyhouses to lengthen the functional growing season for vegetables. To improve marketing opportunities for locally-grown produce. The project coordinator will use funds to establish and operate vegetable production trials in two high-tunnel polyhouses measuring 14 by 70 feet. Three varieties of tomatoes will be used. Yield data, crop growth data, crop value, and costs of production will be recorded.

    The polytunnels were erected in the spring of 1996. Each polytunnel measures 14 feet x 68 feet, with a 5 foot space between each tunnel. This space should be increased to 10 feet for snow removal. One house shifted severely due to heavy snow load and inadequate ground anchors. To relieve the load, the plastic between 10 frames had to be split to allow the snow to fall into the house, which relieved the pressure. The plastic in that house needed to be replaced in the spring of 1998, but this I did not do due to illness that year.

    The first year (1996), both houses received a liberal application of rotted steer manure and composted wood chips. Three varieties were grown: ‘Celebrity’, ‘Paragon’, and Johnny’s ‘361’ – all determinate. There were approximately 175 plants of each variety. The seeds were sown on March 28th in a commercial mix, and then transplanted into a 54-cell flat, and finally, into the polytunnel on May 15 – 18. Each polytunnel is equipped with two 23,000 BTU Kero space heaters, which on most nights would give us a night temperature of approximately 50 degrees F.

    Plants were watered with a soaker hose (3 rows equaling 200 feet of continuous hose or 400 feet to the house). Watering is especially important, as over-watering or erratic watering may be a factor in Blossom-End Rot. Plants were all hand watered weekly with Miracle Gro. The whole house was then mulched with newspaper and hay. The plants were then tied up using the so-called “San Diego” method. From this point on, regular tomato cultural practices were followed with the exception of pruning. However, there was very little, if any, pruning as a determinate tomato was used.

    Regarding pollination, the tunnel sides roll up 3 feet, which allows for cross ventilation, plus there is a door and two windows at the opposite end. This allows for wind-driven pollination. The other method is to tap the stakes, which will vibrate the plants sufficiently to effect pollination. It seems that the best time for this is about noon to 2:30 pm, which generally is the hottest time of the day. Bumble bees and honey bees also contribute to the pollination process.

    As the tomatoes started to ripen, we noticed the onset of Anthracnose, which reduced the crop of saleable tomatoes by at least one third. One possible solution for this disease, which we will try in the future, is to move the house to fresh ground. Our houses were to be moved in the spring, but again, this did not happen because of my illness. It could take as much as two years to clear the ground of this disease. The yield for the 1996 crop was 2,460 pounds for 528 plants. The yield for the 1997 crop was approximately 3,100 pounds for about 480 plants.

    Editor’s note: The project was extended one year to gather additional data and explore the possibility of double cropping with early season crops. Utilizing polyhouses, the project coordinator was able to extend production of high quality tomatoes in northern Michigan by approximately 45 days. The production in the polyhouses at the time included tomatoes, peppers, and sweet potatoes.

    Since October 1997, our research shows that tomatoes and peppers, as well as potatoes do not do well together insofar as the spread of Anthracnose. Also, during this time, increased interest has been generated by the diversity of [high tunnel] crops that have been written up by the media. These include: peppers, cukes, strawberries, raspberries, eggplants, melons, etc. A noted example is Johnny’s seed catalog from Albion, ME, listing varieties of tomatoes for greenhouses and polytunnels which include ‘Monroe’ F1- 67 day, ‘Buffalo’ F1-72 day, ‘Octavid’ F1-73 day, and ‘Azafran’ F1-72 day. All of the varieties listed here are indeterminate. It would be most beneficial for prospective polytunnel growers to obtain Johnny’s catalog as there is almost one-half page devoted to polytunnel tomato culture – very informative.

    Another consideration in the construction of polytunnels is that they might have to be moved to fresh ground for disease control, as mentioned earlier. One width would be sufficient, as long as it is fresh ground. Another consideration [for preventing disease buildup] would be [to grow] an alternative crop such as lettuce or radishes, and short hot weather crops in summer. The prices received for the 1996 crop were approximately $1.50 per pound, or $3.00 per quart. This price held pretty much thru the marketing season. Although the yields were much greater in 1998, we lost about 1,000 pounds due to Anthracnose. The average price received was .75 per pound, due to poor quality. The variety grown in 1998 was ‘Bush Goliath’ from Shumway Seeds. The high prices received in 1997 were due to unfavorable weather in downstate Michigan. We were virtually the only ones with homegrown tomatoes on two retail markets in this area, however, a sound agriculture is not based on other growers’ misfortune.

    The costs for a polytunnel operation are very minimal. Plant cost depends on how you value them, or in other words, the actual cost. The actual cost of producing plants in a 4 inch pot, including heat is about 15 to 20 cents. The same plant purchased retail is approximately $1.25. The plants that are grown for polytunnels are not well known to the public, and I believe that this would restrict sales. Costs for the polytunnels include: heat for polytunnels at approximately $100, stakes with pointed ends measuring 1 inch x 1 inch x 5 feet for determinate plants, cost $25 per hundred, and binder twine (2 balls) cost $30 to $40. This plus water and the plastic covering (amortized) at $200 to cover both houses or $66 per year (1-year plastic will last approximately 3 years with care). All small polytunnels seem to be viable to produce certain crops in frost-prone Zone 4.

    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.