We developed a new culture system to facilitate the indoor use of bedding plants. In this system, lightweight organic culture medium is wrapped in a flat cloth container made of a discarded school uniform. In this study, the composition and volume of culture medium appropriate for this culture system were investigated. Marigold and dianthus planted in coir or a mixture of coir and peat moss grew as well as those in the standard mixed red clay soil, while peat moss alone inhibited growth. Plants grown in the cloth container were slightly smaller than those grown in a usual plastic pot, presenting no problem for practical production. The appropriate volume of the medium was 200 mL or more, because a smaller volume such as 100 mL caused growth inhibition. Fungus often grew on the cloth container, which should be controlled to maintain the commercial value. It was classified as the genus Simplicillium on the basis of ITS sequence analysis.