Paspalum carajasense, an endemic and endangered annual grass found in the canga ecosystems of Serra dos Carajás, Brazil, lacks adequate propagation and conservation data. We assessed its germination and growth in various substrates to support conservation and mineland rehabilitation purposes. Seed germination tests involved soaking in water for 24 h and two KNO3 concentrations (2.5% and 5.0%). Seedlings were grown for 100 days on canga topsoil, mining waste substrate, and a commercial organic substrate. Mining substrates received 0%, 50%, and 100% of Carajás revegetation nutrients due to low fertility. Paspalum carajasense can be sexually propagated and pregermination treatments did not increase germination rates (14%). Seedlings were able to grow in all substrates and showed zero mortality. Plants in fertilized substrates showed similar growth to that on canga topsoil, with significant changes in root and leaf traits. In organic substrates, plants accumulated a larger amount of biomass and produced substantial amounts of seeds with higher germination rates, supporting the feasibility of ex situ cultivation. Therefore, our study provides essential information for the propagation and ex situ cultivation of a rare species of canga ecosystems and highlights the possibility of reconciling the conservation of P. carajasense with mineland rehabilitation.