Flower:

Stalked flowers are single or in a cluster of a few flowers at the top of the stem and at branch tips. Flowers are 1 to 2 inches across with 6 to 12 rays (petals), usually 8, that are typically bright yellow at the tip and maroon at the base, occasionally all yellow. Ray tips have 3 lobes, the center lobe largest and may have a few teeth along the edge. The center disk is maroon with numerous tiny, 4-petaled flowers.

The bracts (phyllaries) cupping the flower head are in 2 series, the inner phyllaries in 2 layers, diamond to egg-shaped, blunt to pointed at the tip, green at the base and yellow to reddish at the tip; the outer phyllaries are in a single row and less than half as long as the inner, lance to narrowly egg-shaped and green. Flower stalks and phyllaries are all hairless.

Leaves and stems:

Leaves are opposite, 2 to 6 inches long, to 4 inches wide, stalkless or short-stalked, and divided into 3 to 5 narrow segments, the lower leaves commonly further divided. The segments are mostly less than ¼ inch wide, pointed at the tip, toothless and hairless. Stems are hairless, usually branched, single or multiple from the base.

Fruit:

Fruit is a dark brown to black, oblong-elliptic seed up to 1/6 inch (to 4 mm) long, lacking a tuft of hairs.

Notes:

As its common name suggests, Plains Coreopsis is native to the Great Plains but is widely available in the nursery trade and sometimes escapes cultivation. It is not considered native to Minnesota, contrary to what the national distribution map shows. It is recognized by the finely divided leaves and flowers with bright yellow rays that are maroon at the base, though the amount of maroon can vary from 0 (all yellow) to 90% (nearly all maroon). The center disk flowers are also maroon, which distinguishes it from other Coreopsis species, and the tiny outer phyllaries can also be a determining factor. The flower color resembles the native Gaillardia aristata (Blanketflower), which has broader, hairy leaves and the rays are much more deeply lobed.