East Texas Greenthread

Differences between Thelesperma flavodiscum and T. filifolium are subtle; they may be better treated as one species.

Annuals, 30–70(–120+) cm. Cauline leaves ± scattered over proximal ⁹/10 of plant heights, internodes mostly 35–100+ mm; lobes mostly linear to filiform, sometimes oblanceolate, (10–)25–45+ × 0.5–1(–2) mm. Calyculi of 7–9 linear to narrowly triangular bractlets 4–6(–8) mm. Ray florets 8; laminae yellow, 12–20+ mm. Disc corollas yellow, often with red-brown nerves, throats shorter than lobes. Cypselae 4–5 mm; pappi 0.5–1.5+ mm. 2n = 18, 20.

Thelesperma filifolium (Hooker) A. Gray var. flavodiscum Shinners, Field & Lab. 18: 98. 1950