Conyza bonariensis

Scientific Name Conyza bonariensis (L.) Cronquist
Synonyms Conyza bonariensis (L.) Cronquist, Erigeron bonariense L., Erigeron floribundus Schultz-Bip.
Common Names English: Flax-Leaved Fleabane, Hairy Fleabane, Asthmaweed; German: Südamerikanischer Katzenschweif; French: Cànem bord; Spanish: Rama negra
Description Hairy Fleabane is an erect branched annual with one or more stems, leafy branches and gray-green herbage, densely strigose and hirsute.


Characteristic Features

Blue-green foliage, very narrow, undulate leaves, and purple-tipped involucral bracts.


Long stems, sometimes branching at the base.


The leaves are alternate, the lower ones oblanceolate, serrate to entire, and short-petioled, and the upper reduced, narrower, smooth-margined, and sessile.

Propagation Organs


The numerous flowers are small, disciform and situated on axillary stems in the upper part of the plant. Each head has numerous (125-180) white pistillate flowers which are tiny and inconspicuous and lack ligules, and 10-20 disk flowers which are white to greenish-yellow. The pappus consists of a few hair-like bristles which are whitish to straw-colored, aging to reddish.

Flowering Period

Almost all year round, mostly conspicuous between May - October.


A collection of achenes with a bristly pappus forming a soft spherical structure. The radiating achenes are attached to a common receptacle and when mature they detach and get dispersed by wind.


Light brown.
Pappus is whitish-beige / straw colored. Germination in autumn.

Viability of Seeds

2 to 3 years.


By seed.



Waste areas and cultivated fields, beneath walls and in cracks in pavements and concrete driveways.


Tolerates poor soil conditions.

Agricultural Importance

C. bonariensis causes severe yield loss in various agricultural crops. Some biotypes are resistant to several herbicides including Glyphosate.


Useful non-chemical contribution to Integrated Weed Management

Shallow cultivation (less than 10 cm (3.93 inch)) is recommended to dislodge plants from the soil. The small, light seeds do not emerge from the soil if buried under more than a few millimeters of soil and are only viable for two-three years after production. Scrapping or disturbing of the soil lightly before weed germination can be an effective mean of control.

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