Abstract: A device and a method for introducing seeds or seedlings into a substrate strand, and to a substrate strand encased by a sheath, and to a system for cultivating plants using a substrate strand. The substrate strand is enclosed by a sheath, and the space enveloped by the sheath is filled with a plant substrate. Openings are introduced into the sheath at a predetermined point, through which openings the seeds or seedlings are inserted into the plant substrate. The advantage of the invention lies in substantial automation of these operations in order to increase the efficiency and cost-effectiveness.