The biodegradable string, as a temporary tie for plants and other vegetation, has at least one oxidizing metal filament cladded with a multilayer paper which is permeable to air and water. For the production of the string material, the paper is a ribbon (4) which is coated on at least one surface (5) with a self-adhesive glue (6). The production assembly has a coating station (9) to apply an adhesive (6) to a surface (5) of a paper ribbon (4). The coated ribbon is dried (17) and is cut into the narrowest possible strips (7) to be wound into bobbins (8,8a). The wound strips are drawn off their bobbins to clad the metal filament core of the string, with a self-adhesive bonding. The coating station (9) takes the paper ribbon (4) from a supply station (10), as a bobbin (11) on a spindle (12). The paper ribbon (4) is drawn over the surface of a coating roller (13), which is partially immersed in a bath (14) containing the glue solution (6). A scraper (15) detaches surplus glue from the coating roller surface, to give a dosed coating application. A vibrator (16) acts on the coated paper ribbon (4), to disperse the glue coating into the paper structure. The coated paper ribbon is dried in a drying tunnel (17), in an elliptical shape. The inner convex surface (19) of the tunnel is against the uncoated side (18) of the paper ribbon (4). The other tunnel surface (23) forms a spaced envelope from the inner sliding surface (19), as a passage for pulsed hot air at 30-200 deg C at a rate of 2-2000 m<3>/hr. against the direction of paper ribbon movement, and as a channel for the movement of the paper ribbon (4). The pulsed hot air is additionally heated by heating (24) at the sliding surface (19). The metal filament for the core of the string is drawn from a supply bobbin, and the cladding strips are drawn from their supply bobbins (8,8A). The metal filament is trapped between two layers of coated paper strips, and the string is wound on to bobbins. The finished string material can be with a number of metal filament cores to be cut into a number of thinner strings.
