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Navajo tea, plains greenthread, stiff greenthread

Habit Annuals (sometimes persisting), 10–40(–70+) cm.
Cauline leaves

crowded to ± scattered over proximal 1/2–3/4 of plant heights, internodes mostly 10–35(–50+) mm;

lobes mostly linear to filiform, sometimes oblanceolate, 5–30(–55+) × 0.5–1(–3+) mm.

Ray florets

8;

laminae yellow to golden yellow (sometimes proximally suffused with red-brown), 12–20+ mm.

Disc corollas

red-brown or yellow with red-brown nerves, throats shorter than lobes.

Calyculi

of 7–8+ linear to narrowly triangular bractlets (2–)4–8+ mm.

Cypselae

3.5–4+ mm;

pappi 0.5–1(–2+) mm.

2n

= 16, 18.

Thelesperma filifolium

Phenology Flowering Mar–Aug(–Oct).
Habitat Disturbed sites on clays or sandy soils, rocky slopes, often on limestone
Elevation 10–2200 m (0–7200 ft)
Distribution
from FNA
AR; CO; KS; LA; MO; MS; NE; NM; OK; SD; TX; WY; Mexico (Nuevo León)
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Discussion

As here circumscribed, Thelesperma filifolium includes plants that others have treated as a distinct species or variety: T. intermedium or T. filifolium var. intermedium, characterized as plants mostly 10–40 cm (versus taller); internodes “relatively short” (versus longer); calyculus bractlets mostly 1/4–1/2 lengths of phyllaries (versus more than 1/2 as long); ray corollas yellow (versus “golden yellow”); disc corollas yellow (versus sometimes red-brown); distribution mostly north and west of the typical form (Colorado, Kansas, Nebraska, New Mexico, w Oklahoma, South Dakota, c and w Texas, Wyoming).

According to A. Cronquist (1980), Thelesperma trifidum (Poiret) Britton has been misapplied (e.g., M. L. Fernald 1950) to T. filifolium.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 21, p. 202.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Coreopsidinae > Thelesperma
Sibling taxa
T. ambiguum, T. burridgeanum, T. flavodiscum, T. longipes, T. megapotamicum, T. nuecense, T. simplicifolium, T. subnudum
Synonyms Coreopsis filifolia, T. filifolium var. intermedium, T. intermedium
Name authority (Hooker) A. Gray: Hooker’s J. Bot. Kew Gard. Misc. 1: 252. (1849)
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