Longwood Blue is a bluebeard, a small shrubby perennial that saves its show for the back half of the season: clusters of true sky-blue flowers set against silvery gray-green foliage when much of the border has gone tired. Bees and butterflies mob it, and hummingbirds check in too.

Plant it in full sun and well-drained soil; sogginess in winter is its one enemy. It flowers on new wood, so cut the whole plant back hard, to about a foot, in early spring. It rebuilds into a 2- to 3-foot mound and blooms on schedule.