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cluster yellow tops

yellowtops

Habit Annuals, to 200+ cm (delicate or robust, glabrate or glabrous). Annuals, perennials, or subshrubs, to 200+ cm [trees to 400 cm] (usually ± succulent, herbage usually glaucous).
Stems

erect.

(often purplish) erect or decumbent, branched distally or ± throughout.

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.

cauline; opposite (decussate); petiolate or sessile (weakly connate to connate-perfoliate);

blades (often 3-nerved) oblong-ovate to lanceolate or linear, margins entire, serrate, or spinulose-serrate, faces glabrous or short-pubescent.

Involucres

oblong and cylindric or angular, 3.8–4.5 mm.

oblong, urceolate, cylindric, or turbinate, 0.5–2 mm diam.

Receptacles

convex, epaleate (“receptacles” of glomerules sometimes setose).

Ray florets

0–1;

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

0–1(–2), pistillate, fertile;

corollas yellow or whitish (laminae inconspicuous).

Disc florets

0–1(–2);

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

1–15, bisexual, fertile;

corollas yellow, tubes shorter than to about equaling funnelform to campanulate throats, lobes 5, ± deltate.

Phyllaries

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

persistent, 2–6(–9) in ± 1 series (linear, concave, or boat-shaped, subequal).

Calyculi

0.

Heads

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

radiate or discoid, usually in tight or loose aggregations in (often flat-topped) ± corymbiform arrays or glomerules.

Cypselae

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

pappi 0.

(black) weakly compressed, narrowly oblanceolate or linear-oblong (usually 10-nerved, glabrous);

pappi usually 0, sometimes persistent, of 2–4 hyaline scales, or coroniform (of connate scales).

x

= 18.

2n

= 36.

Flaveria trinervia

Flaveria

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)]
[WildflowerSearch map]
[BONAP county map]
from USDA
United States; Mexico; Central America; South America; West Indies (Greater Antilles); Asia (India); Africa; Australia
[BONAP county map]
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.)

Species 21 (8 in the flora).

Members of Flaveria are frequently found in alkaline, saline, and gypseous soils, often in disturbed and moist areas. Heads of Flaveria may be either radiate or discoid; when both are present in the same capitulescence, the discoid heads tend to be central and the radiate heads peripheral. Many species of Flaveria have persistent sheathing leaf bases that ring the stems after the leaves have fallen.

Flaveria is notable because certain species exhibit C3 photosynthesis, some C3–C4 (intermediate) photosynthesis, and others (F. brownii, F. bidentis, F. campestris, and F. trinervia in the United States) classic C4 photosynthesis.

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

Key
1. Pappi usually of 2–4 scales or coroniform, rarely 0
→ 2
1. Pappi 0
→ 3
2. Leaf blades to 10–40 mm wide, bases connate-perfoliate; New Mexico, Texas
F. chlorifolia
2. Leaf blades 2–7 mm wide, bases weakly connate; Arizona
F. mcdougallii
3. Heads in tight, axillary glomerules ("receptacles" of glomerules setose)
F. trinervia
3. Heads usually in corymbiform, paniculiform, or spiciform arrays, seldom in tight, axillary glomerules ("receptacles" of glomerules not setose).
→ 4
4. Annuals
→ 5
4. Perennials (annuals)
→ 6
5. Heads in scorpioid cymiform arrays; ray laminae to 1 mm; Alabama, Florida, Georgia
F. bidentis
5. Heads in corymbiform arrays; ray laminae 1.5–2.5 mm; sc, sw United States
F. campestris
6. Calyculus bractlets surpassing involucres (sw coast, Florida)
F. floridana
6. Calyculus bractlets shorter than involucres
→ 7
7. Ray laminae oblong-elliptic, 2 mm; disc florets (5–)7–10; Texas
F. brownii
7. Ray laminae oval to obovate-spatulate, 2–3 mm; disc florets (2–)5–7(–8); Florida
F. linearis
Source FNA vol. 21, p. 250. FNA vol. 21, p. 247. Authors: Sharon C. Yarborough, A. Michael Powell.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Flaveriinae > Flaveria Asteraceae > tribe Heliantheae > subtribe Flaveriinae
Sibling taxa
F. bidentis, F. brownii, F. campestris, F. chlorifolia, F. floridana, F. linearis, F. mcdougallii
Subordinate taxa
F. bidentis, F. brownii, F. campestris, F. chlorifolia, F. floridana, F. linearis, F. mcdougallii, F. trinervia
Synonyms Odera trinervia
Name authority (Sprengel) C. Mohr: Contr. U.S. Natl. Herb. 6: 810. (1901) Jussieu: Gen. Pl., 186. (1789)
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