Erigeron canadensis (L.)

Tall Horseweed
Asteraceae (Sunflower Family)


 

Tall horseweed is an erect, leafy, many-branched annual growing to 6' or 7' tall.  The herbage is subglabrous to stiff-hirsute, and the many leaves are alternate, the lower ones being oblanceolate to 4" long and entire to serrate, and the upper narrower, sessile and entire.  The numerous flowering heads, which appear in terminal panicles, are radiate, and the 25-40 ray flowers have been described as inconspicuous.  I feel that while it is true that the heads are small, only about 3/16" high, the rays are clearly delineated as the above photo shows.  There are also 7-12 disk flowers with pappi of dirty-white, hairlike bristles on each head and involucral bracts which are linear, green, glabrous to slightly strigose, and have a brownish, resin-filled midvein and subscarious margins.  Tall horseweed is extremely common, typically occupying fields, firebreaks, and waste and disturbed areas both grassy and bare generally below 6000', and ranging throughout the United States and southern Canada, and indeed present ± worldwide. It may be seen blooming from June to September.

Click here for Latin name derivations: 1) Erigeron 2) canadensis.
Pronunciation: er-IJ-er-on kan-a-DEN-sis.
Click here for Botanical Term Meanings.
Formerly Conyza canadensis.

 






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