Flora of North America species comparison

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Conyza floribunda

asthmaweed
Habit Plants erect, 30–150+ cm, branched mostly distally.
Leaves

faces sparsely strigose to hispidulous or glabrate (margins ± ciliolate proximally, hairs erect, on nerves);

proximal narrowly oblanceolate to linear, 50–100 × 5–15 mm, toothed or entire;

distal similar, smaller, entire.
Involucres

3–4 mm.
Receptacles

1–2+ mm diam. in fruit.
Pistillate florets

30–40+;

corollas ± equaling or surpassing styles, laminae 0 or to 0.3 mm.
Disc florets

10–20+.
Phyllaries

usually sparsely strigose (at least the outer; margins chartaceous to scarious), outer greenish, becoming reddish brown, lanceolate, shorter, inner stramineous to reddish, lance-attenuate.
Heads

in paniculiform or corymbiform arrays.
Cypselae

pale tan (usually some with reddish nerves), 1–1.5 mm, faces sparsely strigillose or glabrate;

pappi of 15–25 white bristles 2–3 mm.
2n

= 18; 54 or 56.

Conyza floribunda
Phenology Flowering summer–fall.
Habitat Disturbed sites
Elevation 10–100 m (0–300 ft)
Distribution
from FNA
CA; FL; Mexico; Central America; South America; Europe; Asia; Africa [Introduced in North America]
Discussion

Conyza floribunda is thought to be native to South America.

In some floras of the past 50 or so years, Conyza bilbaoana has been treated as distinct from C. floribunda; in others, C. bilbaoana and C. floribunda have been treated as synonyms of C. bonariensis. For some traits (e.g., indument, phyllaries, florets), members of C. floribunda are intermediate to C. bonariensis and C. canadensis; some specimens that I have called C. floribunda may be hybrids. For example, a robust specimen from Santa Cruz Island, California, was originally labeled “C. bonariensis ×canadensis (?).” Locally (e.g., in Berkeley, California), C. canadensis usually comes into flower as C. bonariensis goes to seed. So far as sampled, C. canadensis is diploid; C. bonariensis is hexaploid. Pollen stainability in the Santa Cruz Island specimen is ca. 99%.

If treated as a variety of Conyza bonariensis, the correct name for the taxon treated here as C. floribunda is C. bonariensis var. leiotheca.

Some botanists, e.g., J. B. Marshall (1974), have treated the nomenclatural types of Conyza floribunda and C. sumatrensis (Retzius) E. Walker (= Erigeron sumatrensis Retzius) as conspecific.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 20, p. 350.
Parent taxa Asteraceae > tribe Astereae > Conyza
Sibling taxa
C. bonariensis, C. canadensis, C. ramosissima
Synonyms C. bilbaoana, C. bonariensis var. leiotheca
Name authority Kunth: in A. von Humboldt et al., Nov. Gen. Sp. 4(fol.): 57. (1818)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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