Blue Flax (Linum lewisii)

Prairie Flax (Linum lewisii) usually carries delicate powder-blue flowers on nodding stalks. However, the flowers are sometimes white or lavender. It is a perennial, blooming in summer over a long period. The needle-like leaves make a fine, lacy contrast with the wider blooms. It grows fast to one to one and a half feet tall.

From Calscape