Erigeron bonariensis (L.)

Small Horseweed
Asteraceae (Sunflower Family)


Small horseweed is an erect branched annual with 1-several stems, leafy branches and gray-green herbage, densely strigose and hirsute.  The leaves are alternate, the lower ones being oblanceolate, serrate to entire, and short-petioled, and the upper reduced, narrower, smooth-margined, and sessile.  The numerous flowering heads 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.  Because its flowers are not easy to see, small horseweed is noticed mostly after going to seed.  It is a frequent indeed ubiquitous weed in waste and disturbed areas generally below 3000' and ranges from California to the Atlantic coast.  It was introduced from South America and blooms from June to August.  It has also been called asthmaweed and can grow to 2-1/2'-3' tall.

Click here for Latin name derivations: 1) Erigeron 2) bonariensis.
Pronunciation: er-IJ-er-on bo-nar-ee-EN-sis.
Click here for Botanical Term Meanings.
Formerly Conyza bonariensis.


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