Cabbage seed production in western Washington is at risk from freeze damage in the months of November to February. During the 1987-1988, 1988-1989 and 1989-1990 winters, the cold protection efficacy of 5 floating row covers (Agryl P17, Dewitt N-sulate, Reemay 2014, DuPont Typar, VisQueen Porous Row Cover) and straw was tested on field-grown cabbage. Air temperature in the cabbage crown, Tk50 of cabbage leaves, plant winter survival and seed yield were measured. During a severe freeze in February 1989, an average temperature of -11.1 °C was recorded in the uncovered controls while temperatures under the row covers were -6.7°C, -6.8°C and -8.4 °C under the N-sulate, VisQueen and Agryl covers, respectively. When compared to controls in June of 1989, row covers increased the survival of the more cold hardy `Brunswick' plants but did not significantly increase seed yields. The duration and severity of the February 1989 freeze was such that all of the less cold hardy `Golden Acre' plants were killed.
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