Those look exactly like some kind of wild or feral Iris, the kinds that make either small corms or thin rhizomes.
Iris of these kind have longish, heavy, slightly wide leaves that grow from the base mostly, with a few along the lower half of the flower stalks.
Did you see them in flower? The flowers would have been basically Irish shaped, but with thinner, not as showy sets of petals as the usual domesticated Irises.
Some of these kinds have been bred for gardens and are very beautiful, with nice leaves, and colorful, well formed flowers.