Iris tenax

From Oregon Flora, Gardening with Natives:

Oregon iris' lovely inflorescence rivals ornamental cultivars, its sepals and petals running the gamut from violet to white or creamy yellow. Growing in clumps and spreading moderately through rhizomes, it forms a lovely low groundcover even tolerating dry shade found under conifers. Oregon iris prefers well-drained soil and, once established, it can be drought tolerant. Avoid prolonged wet soils as these can kill the plant. The exceptionally strong fibers from the "tenacious" (epithet: tenax) strap-like leaves can be used for weaving and rope making.