Slender arching stems carrying hundreds of small clear sky-blue saucers, at 30 to 45cm, and the whole plant moves in the least breeze. In a drift it reads as a river of blue running through the border.
Each flower lasts one morning. They open with the sun, drop their petals by late afternoon and leave a scatter of blue confetti on the ground beneath, and a fresh flush opens the next day. That goes on from June through August. It is also one of the few perennials that flowers in its first year from seed, and though it is short-lived at three or four years a plant, it self-seeds reliably enough to hold its place indefinitely once settled.
What kills it is heavy wet clay in winter, not cold. It is hardy well below anything Britain produces and thoroughly drought-tolerant, and it wants sharp drainage above all else; on heavy ground add grit, use a raised bed, or grow it in rockery conditions. It also hates root disturbance, so sow it where it is to grow or raise it in modules. Shear it back by half after the first flush for a second.
