Plants erect, 10-100(-150+) cm, branched mostly distally. Leaves: faces ± densely strigose or hispidulous; proximal blades oblanceolate, 30-80(-120+) × 10-25+ mm, obscurely lobed to coarsely toothed or entire; distal narrowly oblanceolate to linear, 10-50 × 2-10 mm, obscurely toothed or entire. Heads usually in paniculiform to racemiform, rarely corymbiform arrays. Involucres 3.5-5 mm. Phyllaries usually strigose or hispidulous; outer greenish to purplish, lanceolate, shorter; inner stramineous to purplish, linear-attenuate (more chartaceous to scarious, less hairy). Receptacles 3-5 mm diam. in fruit. Pistillate florets 60-150+; corollas ± equaling or surpassing styles, laminae 0 or to 0.3 mm. Disc florets 8-12+. Cypselae pale tan, 1-1.5 mm, faces glabrous or sparsely strigillose; pappi of 15-25+, pinkish, sordid, or tawny bristles 3-4+ mm. 2n = 54.
Flowering year round, mostly late summer-fall. Disturbed sites, along roads and streets; 0-500 m; introduced; Ala., Ariz., Calif., Fla., Ga., La., Miss., N.Mex. N.C., Oreg., S.C., Tex., Utah, Va.; South America.
Conyza bonariensis is widespread in tropical and warm-temperate regions of the world. It is thought to be native to South America.
Duration: Annual
Nativity: Non-Native
Lifeform: Forb/Herb
General: Introduced annual 10-40 cm tall with 1 to several stems from base and corymbosely branching above, herbage hirsute and slightly scabrous, grayish.
Leaves: Linear, numerous, 1.5-4 mm wide, 1.5-9 cm long, shallowly dentate to entire.
Flowers: Heads 6-8 mm in diameter, numerous, corymbosely arranged, peduncles 3-20 mm long, involucral bracts lance-subulate to linear-subulate, 4-6 mm long, greenish, hirsutulous, margins slightly scarious; inconspicuous ray flowers, ligules barely equaling or slightly surpassing pappus, 3-4.5 mm long, disk corollas 3-3.5 mm long, greenish yellow, slender tube 1.2 mm long, lobes narrowly lance-triangular, .2-.3 mm long.
Fruits: Brownish cypselae, 1.2 mm long, faintly compressed, minutely and sparsely stiff hairs to glabrate, pappus bristles capillary 3-4 mm long, tawny or shining white in youth, reddish in age.
Ecology: Found along irrigation ditches, river bottoms and occasionally as a roadside weed below 3,500 ft (1067 m); flowers June-September.
Notes: This is a widespread weed, generally on disturbed, urban sites.
Ethnobotany: Unknown, but C. canadensis has many uses.
Etymology: Conyza is a name used by Theophrastus, Pliny, and Dioscorides, presumably from the Greek konops (flea), bonariensis means of or from Buenos Aires.
Synonyms: Erigeron bonariensis, Erigeron crispus, Erigeron linifolius, Leptilon bonariense, Linnaeus linifolium
Editor: SBuckley, 2010
Annual, 1-10+ dm, copiously and loosely hairy, habitally like no. 1 [Conyza canadensis (L.) Cronquist], or often with some of the lateral branches elongate and overtopping the central axis; lower lvs in robust plants sometimes to 15 נ2 cm; heads larger than in no. 1, the disk often over 1 cm wide; invol 4-6 mm, copiously short-hairy; pistillate fls (50-)70-200+, with a very short or scarcely developed ray to 0.5 mm, this generally surpassed by the style and equaling to more often surpassed by the often tawny or reddish pappus; 2n=54. A weed in waste places, widespread in trop. Amer. and occasionally intr. in se. U.S., n. to Va. Summer. (C. floribunda; Erigeron b.; Leptilon b.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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