Given the right amount of sun, Kalimeris pinnatifida, or Double Japanese Aster, stands from two to three feet high and is smothered in double, one-inch white flowers with buttery yellow centers for a very long time in  summer to early fall.  Not only does this Double Japanese Aster bloom generously, but it is also long lived; I have grown it for many years.   Kalimeris pinnatifida does not reseed, but it is an accommodating spreader and definitely makes its presence known in the garden (but in a very good way).  Sun/partial shade in Zones 6-9.  Quarts.

Kalimeris yomena "Geisha," variegated Japanese Aster, is grown more for its variegated foliage than for its flowers, but there are soft lavender/white, one-inch flowers in the bargain, too. Like its relative, Kalimeris pinnatifida, it is also a spreader, but that's about as far as the resemblance goes. The leaves are larger, jagged, and mottled green and gold, and the flowers are more aster-like than its relative. This perennial grows from two to three feet in full sun (foliage will be more gold in full sun) to partial shade in Zones 6-9. Quarts.