A shoot of a plant is cultivated under the presence of glutathione, so that the shoot is rooted. It is possible to cultivate the shoot under the presence of glutathione by use of a rooting medium including glutathione or by contacting a solution including glutathione with the shoot. Oxidized glutathione is preferably used as glutathione. By promoting rooting of the shoot of the plant, a rooting rate of the shoot of the plant is improved. This improves productivity of a clone seedling.
