Vascular Plants - Asteraceae - Conyza:
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Conyza bonariensis
Page Author: Don Knoke
South American horseweed, South American conyza 
Image © Richard Old
Image © Richard Old
Habit: herb
Duration: annual
Origin: Introduced
Distribution: Introduced from Oregon through Arizona and Texas to Florida
Habitat: Occasionally escapes from cultivation
Species Description:

General: Somewhat hairy, branched annual, 2-10 dm. tall.
Leaves: Leaves numerous, hairy, dark green, narrow, up to 10 cm. long and 2 cm. wide, often slightly wrinkled or distorted.
Flowers: Heads numerous in an open inflorescence, borne on the ends of branches; involucre 6-8 mm. high and 1 cm. wide, short-hairy, its bracts narrow and tapering; flowers white, disk flowers 10-20, ray flowers minute and shorter than the pappus.
Fruits: Achene about one-half the length of the capillary pappus.
Accepted Name:
Conyza bonariensis (L.) Cronquist
Synonyms:
Conyza bonariensis (L.) Cronquist var. leiotheca (S.F. Blake) Cuatrec.
Conyza floribunda Kunth

Treated in Flora of the PNW as:
Conyza bonariensis
Additional Resources:

PNW Herbaria Specimens: View list of Conyza bonariensis specimens in the Consortium of Pacific Northwest Herbaria database.

WTU Herbarium Specimens: View list of Conyza bonariensis specimens in the WTU Herbarium database.

Washington Flora Checklist: Conyza bonariensis treatment.

E-Flora BC: Conyza bonariensis atlas page.

CalPhotos: Conyza bonariensis images.

USDA Plants Database: Conyza bonariensis.
Additional photographs of Conyza bonariensis:
(click on a thumbnail to view larger photo)

Richard Old

Richard Old

Richard Old
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Burke Museum


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Washington Native Plant Society
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