Petroleum-based plastics and synthetic fertilizers are commonplace in container-crop production, and their use raises concerns about the sustainability of plants produced in containers. Bioplastic materials have been developed as replacements that are more sustainable, but their use has been limited to date. Using materials made from composites of soy-based [Glycine max (L.) Merr.] ingredients and commercially-available bioplastics, we fabricated containers and pelletized fertilizers to understand nutrient-release characteristics of soy-based bioplastic composites while producing plants in container-crop production. My first objective was to evaluate the growth and mineral nutritional status of a common greenhouse species [marigold (Tagetes patula L.)] grown in biocontainers that were manufactured with composite bioplastics containing various amounts of a soy-based biopolymer (soy bioplastic) and poly(lactic) acid (PLA) or polyhydroxyalkanoates (PHA). My second objective was to evaluate the usage of soy-bioplastic composites that have been pelletized for use as a biologically-based (bio-based) fertilizer while growing three greenhouse-grown ornamental species [marigold, snapdragon (Antirrhinum majus L.), and cyclamen (Cyclamen persicum Mill.)]. Plants produced in soy-bioplastic composite containers had similar or higher shoot dry mass, as well as nutrient concentration and content, depending on the amount of fertilizer applied. When comparing plants in 50% soy bioplastic-50% PLA containers with plants produced in petroleum-plastic containers, nearly five times as much fertilizer was needed to ensure comparable growth for plants in petroleum-plastic containers. This represents around an 80% reduction in fertilizer needed to produce quality plants in soy-based composite biocontainers. Plants grown with a standard amounts of fertilizer, regardless of fertilizer source, showed similar growth or slightly less growth when fertilized with pelletized soy-bioplastic composites. A point of excess was reached when using any pelletized soy-bioplastic composites at concentrations higher than would normally be applied. In general, soy-based bioplastic composites show potential to replace a portion of the petroleum plastic and synthetic fertilizer used extensively throughout the horticulture industry, but more evaluations should focus on improving performance of bioplastics for use in container-crop production.