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WEED FLORA OF IOWA 



Fig. 198-B.- A patch of Wild Sunflowers (.Helianthus annuus). 



western Iowa. 

 (Photographed by Pammel.) 



Common In 



Prairie Sunflower {Helianthus petiolaris Nutt.). 



Description. — The prairie sunflower is an annual 1-3 ft. high ; 

 lower branches rough; stem leaves 1-3 in. long, oblong to ovate- 

 lanceolate, sparingly toothed, lower leaves abruptly contracted into 

 a long slender petiole; ray flowers yellow, disk flowers brownish; 

 bracts lanceolate or oblong-lanceolate, usually not ciliate; head 

 flowers smaller than in common sunflower; flowers half an inch 

 or more in diameter. 



Distribution. — Prairie sunflower is most abundant in dry prairies 

 from Minnesota to the northwest territory and Oregon and south 

 to Missouri. It has become naturalized more or less in Iowa. 

 It is not uncommon from Council Bluffs to Sioux City and 

 around Muscatine. 



Extermination. — This weed is easily exterminated by cultivation. 



