Lychnis flos- cuculi (Ragged Robin)
I grow Ragged Robin for two reasons: the name, first of all, and the flowers, of course. And who wouldn't be attracted to something called Ragged Robin or White Robin? The flowers resemble some varieties of Dianthus, skinny and twisted, and stand high (about 12 inches) above the grass-like foliage. They are charming in a woodland setting (early to mid-May here in Zone 6) where they will multiply if you're lucky. Sun/partial shade. Zones 6-8. Quarts. (Illustration from Flora von Deutchland, Osterreich und der Schweiz, 1885, from Wiki Commons).