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WEED FLORA OP IOWA 



Pig. 187-A. Distribution of Daisy Fleabane. 



not contain these weed seeds. This weed is easily destroyed by cul- 

 tivation. The meadows are sown from seed coming from the neigh- 

 boring roadside or field. The weeds should, therefore-, be cut in 

 waste places. 



Horseweed (Erigeron canadensis L.). 



Description.— Bristlj, hairy, or sometimes glabrate stem, 1-6 ft. 

 high, simple or paniculately branched ; leaves usually pubescent or 

 ciliate, the lower spatulate, incised or entire, obtuse or acutish, 

 the upper generally linear and entire ; heads- numerous, with in- 

 conspicuous white ray flowers shorter than the pappus; pappus 

 simple; trichomes several-celled, straight with long cells, curved 

 with short cells. 



Distribution. — ^Horseweed is common throughout eastern North 

 America; naturalized in Europe, the Rocky mountains and along 

 the Pacific coast. Everywhere in Iowa in waste places and in cul- 

 tivated fields. 



Extermination. — This weed is an annual and is very easily de- 

 stroyed. Cutting off just below the surface of . the ground will 

 exterminate it, provided, of course, that the new seeds are not per- 

 mitted to re-seed the soil. The weed is common everywhere and 

 the fact that it is so easily blown by the wind makes it difficult to 

 keep it in check. 



