Monitoring Impacts of High Tunnels on Growing Conditions and Season Extension in Southcentral Alaska

This project was funded in 2012 by the Western Sustainable Agriculture Research & Education Producer grant program. Below you can find the project abstracts, a downloadable Excel spreadsheet with all of the raw data collected from the project and links to final project report and documents. Data collected includes inside and outside high tunnel air temperature, soil temperature, and relative humidity. For questions, please contact Rachel Lord at

Project Data

Data from air and soil loggers were collected hourly at 10 high tunnels around Homer and Anchor Point. All raw data are included in this spreadsheet. Homer HT SARE Air Soil Data 2013-2014.xlsx

A report summarizing data collected at all of the participating high tunnels, including site information and growing degree day (GDD) calculations, can be found here.

Project Summary

High tunnels are generally considered to add two to four weeks to a growing season, however there has been little research done in coastal Alaska to ground-truth or better understand this assumption largely developed in the Lower 48 states. Climate in the Homer-area is dominated by cool and wet summers, with dramatic microclimatic differences in temperature and precipitation at varying elevations. Air and soil temperature and relative humidity data were collected hourly inside and outside of 10 high tunnels around Homer, Alaska. Based on our data, we do not see support for the idea that high tunnels alone in this area add two to four weeks of growing season. Season extension activities should likely be concentrated in the fall, and regardless some additional heat source or other temperature control methods (low tunnels, row cover, etc) likely must be employed to protect crops from cold temperatures. Moisture control in the fall is also a challenge that must be addressed. Our data do suggest, however, that high tunnels alone provide a great amount of season ‘enhancement’ – increasing the growing degree days an average of 2,000 over field conditions. In our coastal, sub-arctic climate this is a huge advantage and collective experiences have anecdotally confirmed faster growth rates and increased yields of certain crops. Farmers at higher elevations will likely see greater positive impacts from double-poly tunnels, however added heat retention is likely greater and when using additional heat double-poly tunnels are likely advantageous regardless of the elevation.