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cluster yellow tops

Habit Annuals, to 200+ cm (delicate or robust, glabrate or glabrous).
Stems

erect.

Leaves

petiolate (proximal, petioles 10–20 mm) or sessile (distal);

blades lanceolate or oblanceolate to elliptic or subovate, 30–150 × (7–)10–40 mm, bases (distal) connate, margins serrate, serrate-dentate, or spinulose-serrate.

Heads

30–300+, in tight, axillary, sessile glomerules (receptacles of glomerules setose).

Involucres

oblong and cylindric or angular, 3.8–4.5 mm.

Ray florets

0–1;

laminae pale yellow or whitish, oblique or suborbiculate, 0.5–1 mm.

Disc florets

0–1(–2);

corolla tubes 0.5–1.4 mm, throats campanulate, 0.5–0.8 mm.

Phyllaries

usually 2, oblong (closely investing and falling with mature cypselae).

Calyculi

0.

Cypselae

oblanceoloid to subclavate, 2–2.6 mm (rays longer);

pappi 0.

2n

= 36.

Flaveria trinervia

Phenology Flowering Mar–Dec.
Habitat Near water, saline and gypseous areas
Elevation 0–1900 m [0–6200 ft]
Distribution
from FNA
AZ; CA; FL; MA; MO; NM; TX; VA; HI; West Indies; Central America (British Honduras); South America (Brazil, Ecuador, Peru, Venezuela); Africa [Probably introduced in Asia (India, Middle East)]
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Discussion

Flaveria trinervia is widespread and weedy; it often occurs in saline, gypseous, disturbed areas near permanent or ephemeral water sources in southern Florida and from Texas to southern California. It occurs also in scattered locations in some eastern states and has been reported from Alabama.

The heads of Flaveria trinervia, which usually contain just one floret, are either radiate or discoid; radiate heads tend to occur on the periphery of setose glomerules. Reduction of some of the floral features, including number of florets [0–1(–2)], phyllaries per head (2), and size of ray laminae, suggest that F. trinervia may be the most derived species in the genus.

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

Source FNA vol. 21, p. 250.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Flaveriinae > Flaveria
Sibling taxa
F. bidentis, F. brownii, F. campestris, F. chlorifolia, F. floridana, F. linearis, F. mcdougallii
Synonyms Odera trinervia
Name authority (Sprengel) C. Mohr: Contr. U.S. Natl. Herb. 6: 810. (1901)
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