Frass is the left-over substrate produced from mass rearing insects as food and feed. Black soldier fly (Hermetia illucens) larvae frass has become a popular option for vegetable production as a potential fertilizer and peat replacement. Controlled environment propagation of ornamental crops requires large amounts of peat, therefore researching alternative substrates has a rising interest for growers. Pansies (Viola x wittrockiana), Marigold ‘Inca II’(Tagetes erecta), and Marigold ‘Safari’(Tagetes patula) were grown in growth chambers to evaluate the incorporation of frass into peat based substrates for ornamental production: 3 treatments from previous studies (BSF 10, 20, and 30%), 1 treatment included to assess the impact of leaching on frass (BSF 40-), and a 100% peat control (CP 100%). Pansies grown in the BSF treatments of were statistically comparable to the control in all parameters except, root weight. Pansy root weight was significantly higher in the treated BSF 40- treatment. BSF 40% produced the lowest values in all crops and parameters, except for Marigold ‘Inca’ root weight, where only BSF 40- was significantly higher. BSF 40- was significantly greater or equal to the control in all crops and parameters, except for Marigold ‘Safari’ plant size and root weight. Chlorophyll concentrations were statistically comparable across all treatment and control in all crops. Past research and this study generally indicate that at large concentrations, like 40%, frass can have negative outcomes for crop production in peat based substrates. However, due to the success of our leached treatment, BSF 40-, it seems frass can be utilized at larger concentrations, but additional alterations may be required before mixing into growing medias and substrates. Additionally, certain crops appear to have more neutral and positive reactions to frass incorporation. Engaging efforts to target ideal crops will improve the application and practicality of this research.
