A flat panel 2,3,4 of flexible material for forming a container for growing plants has a first interlock portion 10 at one end and a second interlock portion 11 at the opposite end. The panel 2,3,4 is shapable so that the first and second interlock portions 10,11 are interengagable with each other or with corresponding interlock portions 10,11 of similar panels. In one case the base panel 2 is of uniform height along the length thereof. In another case the panel 3,4 is of variable height along the length thereof. The panel 2,3,4 may comprise a plurality of ventilation slots 22 along the length thereof. The panels 2,3,4 may be used to form a raised bed or a cold frame. The panels 2,3,4 may be mounted one above another and may be used to form a small greenhouse with an adjustable and/or removable roof 6. <；Figure 3>；
