A plant protector comprising a housing of sufficient dimensions to enclose a plant and having a ventilation opening therein. A cover is provided for covering the ventilation opening and a thermal controlled actuator is coupled between the cover and housing for moving the cover between a closed position at lower temperatures where the cover is positioned over the opening and an open position at higher temperatures where the cover is not positioned over the opening. The cover may be pivotally mounted on the housing and the actuator is preferably located between the cover and housing adjacent the pivot.