Ecological rehabilitation of degraded mining sites is necessary and possible by reintroducing pioneer manganese-accumulating plants. From the Mn-enriched biomass, our group has developed a process to recycle plant-derived metallic elements into innovative polymetallic catalysts, called Eco-Mn ecocatalysts. These first biosourced Mn-rich catalysts have demonstrated competitive catalytic activity in green organic synthesis. To expand the use of these catalysts in organic chemistry, their catalytic activity has to be correlated with their structure and properties. Thus, we put forward for the first time an extensive structural study of Eco-Mn catalysts, including composition analysis, crystalline structure analysis, and chemical environment around active catalytic center (manganese and iron) analysis. Density Functional Theory (DFT) calculations support our conclusions. Finally, this study highlights the peculiar vegetal footprint of Eco-Mn catalysts.