The removable covering comprises a flexible sheet (5) which is wound, from a top point to a low point and vice versa, in an open section (10) mounted on a carriage (1) which is displaceable on the greenhouse framework. The sheet is fixed to an internal winding tube which is mounted in the open section. Displacement of the open section with the carriage causes rotation of the winding tube. When the open section is displaced towards the bottom it causes winding of the sheet. Displacement upwards causes unwinding of the sheet, which is fixed at its end opposite to that which is fixed to the winding tube. Rotation of the winding tube in the open section is obtained by a rack-and-pinion system. The pinion is fixed on the winding tube and engages with the carriage and the rack, fixed on the side frame of the greenhouse.
