The apparatus comprises a delumper-sifter and a mixer used to prepare a mixture of peat and water which is placed in storage; the mixture is then passed to a forming device, is extruded in the form of continuous cylinder and is covered with a sheet of degradable paper; the covered product is cut up by means of a rotating spiral cutter, the rotational speed of which is synchronized with the speed at which the mixture emerges from the forming device, thus making it possible to obtain cylindrical extrusions of a predetermined length; the cut extrusions pass to a conveyor-distributor which arranges them in rows and then allows them to fall, in a vertical position, onto a supporting conveyor above which a drum, equipped with cylindrical protuberances, produces in the extrusions cavities in which seeds are subsequently placed and covered with sand; the final operation carried out by the apparatus is to group the seedling tubes thus produced and to wrap them in packages.