Peroxidases have a wide range of applications in biotechnology and other industry. The source of peroxidase is thus very important. In this study, we employ a fluorescence spectroscopy device that is common in many undergraduate physics laboratories to investigate peroxidases from three common but poorly studied plant sources for their best physicochemical conditions for activity and stabilities. We report on the optima conditions with respect to temperature, thermal stability and pH that are determined by monitoring the hydrogen peroxide-dependent oxidation of guaiacol. This study reveals which of the three plants holds the best promise as a source of peroxidase for applications.