Flower:

Flowers are in open branching clusters at the top of the plant. Individual flowers are about 1 inch across with 15 to 30 light blue to purple petals (ray flowers) and yellow center disc flowers that turn reddish with maturity.

The bracts behind the flower are narrow and slightly spreading, often with a dark tip.

Leaves and stem:

Leaves are smooth and almost waxy, mostly toothless, mostly hairless, and mostly clasp the main stem. The shape can be variable, from somewhat spatula shaped to rounded at the base and tapering to a pointed tip.

Leaves near the base of the plant are largest, up to 4 inches long and 1½ inches wide, and may wither away by flowering time; they become smaller as they ascend the stem. Attachment is alternate. The main stem is hairless and may be green or reddish.

Fruit:

Fruit is a dry seed with a tuft of light brown hair to carry it off in the wind.

Notes:

Smooth Blue Aster is similar to Sky Blue Aster and grows in a similar habitat, blooming at about the same time. The leaves of Sky Blue Aster are arrowhead shaped near the base and do not clasp the stem, its flowers are generally smaller, less than 1 inch across, and its bracts are flattened and diamond shaped.