Flower:

Branching clusters of short-stalked flowers at the top of the stem and arising from upper leaf axils. Branches are often widely spreading with the flowers all on one side of the branch (secund) or forming a cylindrical cluster. Flowers are about ½ inch across with 9 to 16 petals (ray flowers) and a creamy white to pale yellow center disk that quickly turns purplish. Ray color is white, rarely pinkish or violet.

The bracts (phyllaries) surrounding the base of the flower are in 3 or 4 layers, usually appressed, sparsely hairy, light green with a darker green, lance to diamond-shaped tip. Flower stalks are up to 1/3 inch long and hairy, with 1 to a few leaf-like bracts below the flower.

Leaves and stems:

Leaves are thin, mostly lance-elliptic, ½ to 6 inches long, up to 1½ inch wide, and mostly stalkless. Basal leaves are broader and more variable in shape—from spatula-shaped to nearly round—with winged, sheathing stalks; basal and lower stem leaves wither away by flowering time. Leaves become more lance-linear as they ascend the stem.

The upper leaf surface is smooth to slightly rough, the lower is smooth except for short hairs along the midvein. Edges may be toothless or with shallow teeth, sometimes just around the tip end.

Stems are single or multiple from the base, erect to ascending or sometimes arching, initially green often turning red later in the season, and covered in soft, white hairs, though may become hairless on the lower stem.

Fruit:

Fruit is a dry seed with a tuft of dull white to pinkish hairs to carry them off in the wind.

Notes:

There are a number of asters with small, white flowers in Minnesota and it can be a real challenge to keep them straight. Calico Aster is distinguished by a combination of characteristics: smaller than average flower size (~½ inch), fewer rays than most other white asters (9 to 16), creamy white or very pale yellow center disk (not bright yellow), generally lance-elliptic leaves with hairs only along the midvein on the underside, and stems covered in soft, white hairs. By comparison with other white asters having a generally similar leaf shape, Northern Bog Aster (Symphyotrichum boreale), Panicled Aster (S. lanceolatum), Ontario Aster (S. ontarionis), and Awl Aster (S. pilosum) have flowers with more than 15 rays and brighter yellow disks. In addition, Northern Bog Aster and Panicled Aster have leaves that are hairless except around the edges and only lines of hairs on the stems. Ontario Aster and Awl Aster may have similar branching as Calico Aster as well as stems covered in hairs, but where Calico Aster has hairs only along the leaf midvein, the other two are also hairy on one or both leaf surfaces.