The winged bean (Psophocarpus tetragonolobus) is a tropical legume named for the four frilled, ribbon-like wings that run the length of its pod, giving a cross-section the shape of a four-pointed star. Almost the whole plant is edible — the crisp young pods, the leaves, the sky-blue flowers, the high-protein seeds and the starchy, protein-rich tuber — which has earned it the nickname "the soybean of the tropics."