Season Extension

Season extension techniques to grow year-round can provide higher incomes and increased quality to your fresh-market farm. From growing earlier in the spring, cool season crops in the summer, and continuing production into the fall and winter months, the following publications will outline different approaches to a successful, and longer, season. A good place to start for an overview on the different techniques is ATTRA’s Season Extension Techniques for Market Gardeners. Specifically this publication looks at cultural practices to modify the microclimate where crops are grown (without the use of a structure), the use of plasticulture (plastic film mulches, drip irrigation tape, row covers, low tunnels, and high tunnels), and the economics of season extension. Further resources are provided at the end as well as Appendices regarding high tunnel design and construction.

High Tunnels and Greenhouses

For specific information on hoop houses/high tunnel conditions see The High Tunnel Environment-Internal and External out of the University of Minnesota Extension. It specifically covers light, wind, and temperature factors in the high tunnel. This publication includes information on day length, approximate temperatures for best crop growth, temperature and growing degree-day comparisons between a high tunnel and outside, and the use of freeze covers. The values presented are based on data taken in Grand Rapids, Minnesota. A fact sheet on plastic mulches is provided at the end.

For insight into another farm’s experience with high tunnels, see the case study Blue Gate Farm High Tunnels series, which cover three growing seasons utilizing high tunnels on Blue Gate Farm’s CSA/fresh-market operation. The three publications look at their profitability based on revenue per crop, potential revenue, and production costs including the high tunnel construction. By continuing documentation, it illustrates changes, and additions made in response to particular setbacks, or desired increased production.

Michigan State University’s Greenhouses for Local Food and Farming is an introduction for growers to the principles of in ground, organic vegetable production in unheated greenhouses. Key considerations as well as management recommendations are presented in two parts: building and growing for both beginning and experienced audiences.

Supplemental heating is often needed for cloudy days and cooler nights when growing in a greenhouse. Information on greenhouse heating options can be found in the University of Wisconsin-Extension’s Greenhouse Unit Heaters: Types, Placement, and Efficiency. It discusses differences between unvented, gravity-vented, power-vented, separated combustion, and high efficiency unit heaters along with how heated air distribution can affect energy usage.

Additional Resources and Citations

Adams, Stacy A. and Kim Todd. 2014. Cold Frames, High Tunnels, and Greenhouses: Choose a Growing Structure Best for You. University of Nebraska–Lincoln Extension

Bachmann, Janet. 2005. Season Extension Techniques for Market Gardeners. ATTRA

Beebout, Jill and Sean Skeehan. 2009. Blue Gate Farm High Tunnels Take 2. Practical Farmers of Iowa

Beebout, Jill and Sean Skeehan. 2010. Blue Gate Farm High Tunnels Take 3. Practical Farmers of Iowa

Biernbaum, John A. 2006. Greenhouses for Local Food and Farming. Michigan State University

Sanford, Scott. 2006. Greenhouse Unit Heaters: Types, Placement, and Efficiency. University of Wisconsin Extension

Wildung, David and Pat Johnson. 2004. The High Tunnel Environment-Internal and External. University of Minnesota

Worley, Sally. 2008. High Tunnels: Are they Lucrative? Blue Gate Farm offers its data. Practical Farmers of Iowa