Extending the Strawberry Season: High Tunnels, Low Tunnels, and Targeted Supplemental Heating

Demand for fresh local strawberries continues to increase with the expanding local food movement. However, environmental conditions in many areas are less than ideal for strawberry production.  In many regions of North America with a continental climate, frequent spring frost events result in loss of early blossoms.  In the arid Intermountain West, sprinkler irrigation is not a frost protection option. The effects of five frost protection methods were compared over two seasons for plug, bare-root dormant, and fresh dug plants of ‘Chandler’ and ‘Seascape’ strawberry in North Logan, UT (lat. 41.74°N, 1460 m elevation).  Treatments were: high tunnel, low tunnel, high tunnel + low tunnel, low tunnel with in-ground supplemental heating, and high + low tunnel with in-ground supplemental heating.  Plants were evaluated for runner and branch crown formation, as well as early and total yields. Highest total yields were achieved in the high + low tunnel combination with no significant difference between those with and without supplemental heating. ‘Chandler’ plug, ‘Chandler’ dormant, and ‘Seascape’ dormant gave the highest total yields, with no significant difference among the three. Fresh dug plants yielded far below both plug and dormant plant types in all treatments, most likely due to insufficient crown development (2.3 crowns/plant compared to 5.4 and 6.0 crowns/plant for plug and dormant, respectively).  ‘Chandler’ early yields (before 22 May) were higher than ‘Seascape’ for both plug and bare-root dormant plant types in all treatments. In-ground supplemental heating of 15 °C moved production 5 weeks earlier than the unheated high tunnel treatment and 9 weeks earlier than the outside control. For Utah cold-climate production, a combination of high and low tunnels is most effective in providing frost protection and advancing the season. In-ground supplemental heating can widen the production window but analysis is needed to determine the economic viability of this option.