Plains Coreopsis in a ditch by the Sweet Marsh near my home in northeast Iowa. Photo taken As Is using my Canon PowerShot SX20 IS.
Aster family (Asteraceae)
Description: This is an introduced annual wildflower about 1½–3’ tall that branches occasionally. The stems are medium green and glabrous. The leaves are up to 6" long and 4" across (excluding the petioles); they are simple- or double-pinnate, medium green, and glabrous. The leaflets (or lobes) are up to 2" long and less than ¼" across; they are linear, linear-lanceolate, or linear-oblanceolate. The upper stems terminate in flowerheads that individually span about 1-2" across. Each flowerhead has 6-12 ray florets that surround numerous disk florets. The ray florets are reddish brown toward the center of the flowerhead, but become golden yellow toward their tips; less often, they may be reddish brown throughout. Each ray floret becomes wider toward its tip, which is divided into 3 large teeth. The tiny disk florets have corollas that are reddish brown and tubular in shape; each corolla has 4 tiny teeth along its upper rim. The base of each flowerhead is surrounded by glabrous brown bracts (phyllaries); the outer bracts at the very bottom of the flowerhead are small and triangular in shape, while the inner bracts are much larger in size and ovate in shape.
The blooming period occurs from mid-summer to early fall and lasts about 1-2 months. The fertile disk florets are replaced by small achenes that lack tufts of hair. The root system is fibrous. This wildflower reproduces by reseeding itself.
Cultivation: Preferred growing conditions consist of full sun and moist to mesic sandy soil. However, other kinds of soil are readily tolerated, including those that contain loam, clay-loam, or some gravel. Depending on the cultivar or local ecotype, there is considerable variability in the size of flowerheads and the height of plants.
Range & Habitat: Plains Coreopsis has naturalized in scattered locations. This introduced species is native to the region of the Great Plains in North America. Habitats include sand prairies, rocky glades, areas along railroads, roadsides, and waste areas, particularly where the soil is rather barren. This species is cultivated in gardens because of the attractive flowerheads.