We Grew Tomatoes in January without Heat, But Don't Tell the Farmers

Three years of studies have been conducted at Crystal Springs, MS, to assess the value of secondary row covers for additional climate modification in high tunnels.  The system includes unheated high tunnels, with manual ventilation controls and row covers that are placed over the row covers on cold nights or during particularly cold days.  The covers are placed or removed, and the tunnels opened or closed based on a detailed protocol based on actual and forecast air temperatures in and outside the tunnels.  Crops are sown in the fall, grown through the winter, and terminated in late winter or early spring.  The model vegetable crop in the system was tomatoes.  In the first season, unusually cold weather killed the crop before any fruit could be produced.  In the second and third year, tomatoes were produced and harvested in January and February in treatments with the row covers, despite air temperatures outside the tunnels falling below –7 °C for at least one night.  From these results, we conclude that row covers can extend the range of crops that can be grown in southern U.S. high tunnels.  Although the system has produced valuable information on tunnel temperature behavior and the potential for broadening the range of crops grown during colder portions of the winter, we believe the system of internal covers and crop selection and timing needs further refinement and local testing by research and outreach professionals.  We are not ready to recommend the system to growers as a commercial tomato production practice at this time.