Thermally responsive ventilated cold frame

A cold frame comprising frame means including end walls and side walls, a cover mounting frame pivotally mounted on said frame means and movable through a plurality of positions opening and closing said cold frame, a cover member of light-transmitting, flexible sheet material of sufficient thickness and stiffness to cause the cover to assume a generally arcuate configuration when the ends thereof are constrained at a distance less than the length of said cover member, said cover member being connected at one end to one of said end walls and at the other end to said cover mounting frame at a distance less than the length of said cover member whereby said cover member will assume a generally arcuate unsupported configuration in a closed position of said cover mounting frame, said closed position being defined when said cover mounting frame is in adjacent mating relationship to the other end wall, said side walls having edges formed to be complementary with the configuration of said cover member when said cover mounting frame is in said closed position and engageable with said cover member when said cover mounting frame is in said closed position to define an enclosed space, and thermally responsive actuator means for rotating said cover mounting frame to flex said cover member and move said cover member relative to said side walls and to provide at least one ventilation opening between said side walls and said cover member for said enclosed space.