Edible flowers are a rich source of phytochemicals with potential health benefits. Yet, changes in production practices can influence the phytochemical composition of edible flowers. Practices such as the addition of biochar have been used to affect growing media properties as well as to conserve peat resources. However, there is little known about how biochar affects the phytochemical composition of edible flowers. To determine if biochar affects phytochemicals in Viola cornuta, four cultivars were subjected to different rates of biochar, with and without fertilizer. At the rate of 10% biochar and without fertilizer application, flower polyphenol and flavonoid concentrations were decreased by 10–20% in two cultivars. However, at 25% biochar, flower polyphenol concentrations varied widely. When fertilizer was added, no effects of biochar were seen. Phytochemical characterization of unfertilized plants further revealed that while increased rates of biochar reduced concentrations of certain antioxidant compounds, these compounds were increased when fertilizer was added. Overall, fertilization can counteract some of the negative effects of biochar on Viola cultivars, resulting in higher nutritional quality and an increase in bioactive compounds produced, providing an ability to replace the peat moss with biochar
