Sky-white Aster? Say what? Maybe you've heard of Sky-blue Aster (Aster azureus, or Aster oolentangiensis, or Symphyotrichum oolentangiense, depending on who you listen to), but how about Sky-white Aster?
Okay, so I made up the common name, but it seemed silly to call a plant with nothing blue about it Sky-blue Aster. This is the form of Sky-blue Aster with white ray flowers, known as Aster azureus forma albidus (azureus, of course, means "bright blue"; albidus means "white"). This year must have been a good year for white-flowered forms of composites (Asteraceae); earlier in the year, I posted on Get Your Botany On! about two normally pinkish-purple-flowered species of Liatris with white-flowers. Just to prove that this is in fact Sky-blue Aster, I've included a photo below of the characteristic heart-shaped, rough-textured lower leaves from the plant.
A photograph showing the typical color of the ray flowers of Sky-blue Aster is shown below. Sky-blue Aster is a plant of open to semi-open areas with sandy, loamy, or rocky soils, where it is found in prairies, glades, barrens, savannas, alvars, and open woodlands. It is known from a good part of the eastern half of North America, to as far west as South Dakota and Texas, but is absent from the northeast and the Appalachian region.