Plant protection device in the form of a weather protection extensible over the cultivation. The protection device including a framework (12) consisting of longitudinal and traverse support elements (13, 14) within which at least one waterproof foldable plant protection curtain (16) is extensible from a folded up position and vice versa. The invention also refers to a foldable curtain as a plant protection for cultivations, which curtain (16) has a high tensile strength in it's longitudinal and traverse directions and which via connectors (29) is hung up on a number of support lines (30) stretched across the curtain. The curtain is extensible from a folded up position to an extended position and vice versa, whereby the curtain includes a framework (18) consisting of strips or ribbons and/or lines. The curtain (16) is made of a waterproof laminate and is including relative to the curtain movable stretch or reinforcing lines (22) in essentially parallel rows stretching along the curtain's length. The curtain is provided with a device which in the extended position of the curtain form channels (36).