Coreopsis nuecensis A. Heller, a Texas endemic, was collected by O. A. Farwell in 1925 (7455, BLH, as C. coronata). It was a waif, with C. tinctoria, in a field by a railroad at Flat Rock, Wayne Co. There is some question as to whether seed had been planted at the site, and the evidence is not strong enough to treat it as part of our flora.
1. Phyllaries of outer series all or mostly less than 2.5 mm long; disk flowers 4-merous, red-purple; ray flowers less than 1.5 cm long, usually red-purple on basal half, otherwise yellow, and 3-lobed apically; achenes wingless.
1. Phyllaries of outer series (2–) 2.5–6 mm long; disk flowers 5-merous, yellow (becoming red-brown in C. tripteris); ray flowers ca. 1–2.6 (–3) cm long, yellow, entire or (3–) 4–5-toothed apically; achenes winged.
2. Leaves (except often the uppermost) deeply palmately lobed or trifoliolate (the leaflets sometimes deeply lobed); rays ± elliptic to narrowly obovate, entire or nearly so at apex.
3. Leaves apparently sessile or nearly so (petiole short and winged), with 3 (–5) narrow linear-lanceolate lobes; outer phyllaries nearly as long as the inner.
3. Leaves petioled, compound (3 lance-elliptic leaflets or with central one deeply lobed); outer phyllaries usually about half as long as the inner, or shorter.
2. Leaves unlobed (or some with narrow pinnate lobes); rays cuneate, with (3) 4–5 ± irregular apical teeth.
4. Stem with 4–6 nodes, these (and hence pairs of leaves) extending above middle of the plant (the peduncles, from heads to uppermost leaves or bracts, therefore mostly shorter than the rest of the stem); leaves (at least some of them) with (1–) 2–4 (–7) pairs of lateral lobes.
4. Stem with 2–4 (–5) nodes, these (and hence pairs of leaves) all on lower half of plant (the peduncles therefore longer than rest of the stem); leaves unlobed.