Utilizing carbon materials derived from sustainable biomass on supercapacitors has become particularly attractive recently. High-performance activated carbons (ACs) based on inexpensive, abundant but un-wanted natural wastes are highly preferred. Using dry elm samara as the prototype, demonstrated that three-dimensional (3-D) scaffolding frameworks of highly porous carbon nanosheets(PCNSs) can be derived from plant wastes having specific natural morphology,i.e. half-transparent thin flakes, through a facile carbonization and activation treatment. The products possess a high accessible surface area induced by the 3-D framework, and a high density of micro-pores, which benefit large ion storage and high-rate ion transfer. In addition to the electric double-layer capacitor, the heteroatom doping evokes the faradic contribution. This work provides a clear strategy on how to select promising plant-waste candidates for high-performance ACs applied on energy storage.