Flower:

Branching clusters of stalked flowers at the top of the stem and arising from upper leaf axils. Flowers are about 1 inch across with 20 to 35 petals (ray flowers) and a yellow center disk that turns reddish with age. Ray color is very pale lavender (nearly white) to light blue-violet.

The bracts (phyllaries) surrounding the base of the flower are in 4 to 6 layers, lance-oblong to linear, light green with a lance to elongated diamond-shaped darker green tip that is appressed or spreading. Phyllaries are hairless except for a few minute hairs around the tip edge. Flower stalks are up to ¾ inch long, hairy in lines, with several leaf-like bracts below the flower.

Leaves and stems:

Leaves are mostly lance/spear/spatula-shaped, the blade coarsely toothed, sharply pointed at the tip, abruptly narrowed at the base to a toothless, broadly winged stalk that is slightly enlarged at the base into a pair of lobes (auricles) that clasp the stem. Leaves are hairless except for a few hairs on the midvein on the underside. Basal leaves have slender, narrowly winged stalks and wither away by flowering time along with the lowest stem leaves. Most stem leaves persist through fruiting.

In the upper stem, leaves quickly change shape, become stalkless and more generally lance-shaped but still auricled and clasping, becoming smaller and toothless or nearly so as they ascend the stem, with the uppermost leaves reduced to bracts. Stems are mostly single, sometimes multiple from the base, ascending to erect but may be floppy in the upper plant, green or purple, hairless on the lower stem and hairy in lines in the upper plant. Stems often zig-zag between the leaf nodes, hence the common names. Plants may form colonies from creeping rhizomes.

Fruit:

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

Notes:

The leaf shape of Crooked Aster is pretty unique and makes it easy to identify in the field. While Big-leaf Aster (Eurybia macrophylla) also has light blue-violet flowers and broadly winged leaf stalks that clasp the stem, its leaves are much broader and variable in shape as they ascend the stem, most with heart-shaped bases.