Evaluation of Season Extension Covers in Higher Elevation (6500+ ft) Growing Areas

There is an increased demand for local food production at the home gardener and commercial levels.  There is also increasing concerned about food insecurity in the mountains of Colorado.  Rural communities and those in areas with extremely short growing seasons rely almost exclusively on fresh produce and other food items trucked into the area.  Increasing local production of crops will make areas more food secure.  Season extension techniques will play a large role in crop production at high elevation areas with extremely short (~60-120 day) growing seasons depending on elevation and microclimate.

Three season extension techniques were compared in three high elevation counties (Eagle, San Miguel, and Teller counties).  Raised beds (>22 inches tall, 4’ wide x 12’ long) were used at all locations.  Crop yields under flexible 3.5 mm polyethylene covers with automatic vents, and mini-hoops covered with an under layer of spun-bonded polypropylene row cover fabric and a top layer of polyvinyl alcohol film were compared to an uncovered bed.  Plants tested in 2011 through 2013 included lettuce and transitioned to cold-hardy greens (spinach or kale) in the fall.    Fresh yield weights were recorded and monthly photographs taken of each test plot.  Air temperature and soil temperature in each test plot were monitored for the length of the trial using automated data loggers.

Overall, yield and quality were highest in lettuce grown under the double layer of spun-bound polypropylene row cover fabric and polyvinyl alcohol film.  Results for yield and quality for fall and winter greens are not conclusive for either treatment.