A multitude of curled fibers (12) of a biodegradable material like coco fibers, is accommodated inside a rectangular cover (14) made also of a biodegradable material. The roots (16) of the young plants (17) are guided through the meshes of the upper layer of the grid (14) and held in position by the curly fibers (12). The material of the grid (14) and the fibers (12) turn into compost at different times in order to still provide a slight support when one of the two components (12, 14) has vanished.
