Flower:

Branching clusters of stalked flowers at the top of the plant. Flowers are petal-less (rayless), appearing perpetually budding, about 1/3 inch tall, typically a creamy white, sometimes pinkish. The numerous bracts (phyllaries) surrounding the flower are in 3 or 4 layers, hairless, mostly linear with sharply pointed tips, the outer layers widely spreading, the inner ascending to nearly erect. Flower stalks are hairless and up to 1/3 inch long. Flowering branches are ascending or may be prostrate but rising at the tips (decumbent).

Leaves and stems:

Leaves are mostly linear, 1 to 3 inches long, less than ¼ inch wide, hairless, mostly toothless but sometimes with minute teeth, and stalkless. Basal leaves are stalked and more spatula shaped but wither away by flowering time, along with the lower stem leaves. Stems are erect to ascending and hairless.

Fruit:

Fruit is a dry, hairy seed with a tuft of dull white to pinkish hair to carry it off in the wind.

Notes:

Rayless Aster isn't considered native in Minnesota, though it is just to our west in the Dakotas, where it's found in salt marshes, waterways with fluctuating water levels, and waste grounds. While the leaves are very similar to both Heath Aster (Symphyotrichum ericoides) and White Prairie Aster (S. falcatum), both are perennials, have rayed flowers, and are distinctly hairy where Rayless Aster is an annual, essentially hairless, and of course lacks rays on the flowers.