Abstract: A support device for rigidly holding an upright prop driven into a ground mixture in a container having an upper rim. The device comprises an elongated member provided at one end with a ring in which the prop may be slid and held substantially vertically when it is set in ground mixture. The device also comprises a sleeve that can be clipped onto the rim of the container, the sleeve slideably receiving the elongated member and holding it in a direction perpendicular to the rim. The elongated member is detachably locked within the sleeve by a pawl which projects from the sleeve in such a manner as to engage a notch being part of a series of spaced apart notches made in the elongated member.