Annuals, 10-50+ cm. Aerial nodes proximal to first peduncle usually 5-10+, distalmost 1-3 internodes 4-7(-10) cm. Leaves: basal and cauline on proximal 3/4-7/8 of plant heights; petioles 8-35(-120) mm; blades simple or 1(-2)-pinnately lobed with 3-9+ lobes, simple blades or terminal lobes elliptic or lanceolate to oblanceolate or linear, 25-55+ × (1-)2-9(-20) mm. Peduncles 6-15+ cm. Calyculi of lance-deltate to linear bractlets 6-9(-12+) mm. Phyllaries lance-ovate, 7-9+ mm. Ray laminae yellow, usually each with a proximal, red-brown to purple spot or band, 15-20+ mm. Disc corollas 3-4 mm, apices red-brown to purple. Cypselae 1.2-1.8 mm, wingless (margins ± inrolled adaxially, ± corky). 2n = 26.
Flowering Apr-Jun. Sandy soils in open, often disturbed, places; 10-300+ m; Ala., Ark., Fla., Ga., La., Miss., N.C., Okla., S.C., Tex.
Plants in the western part of the distribution of Coreopsis basalis usually have narrower lobes of leaf blades and narrower outer phyllaries; such plants have been treated as C. wrightii or as C. basalis var. wrightii.
A usually smaller sp. with 5-toothed disk-cors and with the outer invol bracts half to fully as long as the inner, is occasionally found in our range as an escape from cult.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.