Coreopsis delphiniifolia Lam.

Plants treated here as Coreopsis delphiniifolia are questionably distinct from C. major. In 1976, E. B. Smith suggested that members of the taxon he called C. ×delphiniifolia may be hybrids or progeny of hybrids involving C. verticillata and C. tripteris and, possibly, C. major. A problem with such an interpretation is that although all of the 35 or so records for C. delphiniifolia in the sense of Smith map at or near known localities for C. major, all but 2 are from well south of the known distribution of C. verticillata and only 3 are from near known localities for C. tripteris.

Perennials, 30–90 cm. Internodes (± mid stem) 3–8 cm. Leaves: petioles 0–1 mm; blades simple or 3-foliolate, simple blades or leaflets usually narrowly lanceolate to lance-linear, 35–80 × 2–5(–7) mm (seldom lobed, sometimes parted into 2–3+ lance-linear to ± linear lobes). Peduncles 15–45+ mm. Calyculi of 8–10 linear bractlets 3–5(–7) mm. Phyllaries 8, oblong-ovate, 5–6+ mm. Ray laminae 15–25(–30) mm. Disc florets 25–60+; corollas yellow (often drying blackish), 5–6 mm. Cypselae oblong, 4.5–6 mm. 2n = 52, 78, 104.