Lychnis chalcedonica (Maltese Cross)
Vermilion, cross-shaped flowers clustered at the tops of stems from two to three feet tall make this plant really stand out in the perennial garden. Although Lynchnis chalcedonica is listed in North American native wildflower books, it was actually introduced to this country from Asia. The species name refers to Chalcedon, an ancient town on the Bosporus, where the flower is said to occur. This old-fashioned favorite isn't seen very often in gardens anymore, but it should be. Sun, Zones 6-8. Quarts.
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).
Lychnis miqueliana (Japanese Woodland Catchfly)
This lovely native to Japan's woodlands was new to my garden last year. Although it is said to be "compact" and is in my garden, I understand that Lychnis miqueliana grows from 18 to 24 inches tall. It is best suited to the woodland garden, as it prefers full or partial shade, but it can withstand a few hours of morning sun. Japanese Woodland Catchfly will go dormant if stressed by heat and drought, so keep that in mind when choosing a planting site. The one-inch coral/red, cross-shaped flowers are quite showy, as is the burgundy-tinted foliage. Zones 5-9.