A method includes inserting viable, in vitro cultivated plant material into an empty pocket of a strip element that is formed at least in part of biodegradable material. The strip element has a first and second wall-forming member arranged to at least partly overlap in a longitudinal direction and to not fully overlap in a transverse direction with the first wall-forming member extending past the second wall-forming member. The wall-forming members are fixed to each other along a bonding line to delimit a plurality of pockets and a plurality of spacer areas in an alternating arrangement along the longitudinal direction such that a top side of each pocket is open. The method includes facilitating, without the use of a substrate, at least one of an acclimatization or a root formation of the in vitro cultivated plant material in the plurality of pockets of the strip element.