346 



WEED FLORA OP IOWA 



Extermination. — It is certain that cultivating the young plants 

 followed by three or four other similar treatments will remove the 

 weed in one or at most two seasons. It would be well to use clover, 

 planted as a rotation after the field had had clean cultivation. 



Artichoke {Helianthus tuberosus L.). 



Description. — A pubescent or hirsute perennial with tuberous 

 underground stems; leaves oblong-lanceolate or ovate-acuminate, 

 scabrous, minutely pubescent; flowers yellowish, large. 



Distribution. — Common from New York to Minnesota; in Iowa 

 most abundant in the northern counties; particularly troublesome 

 in Mitchell, Howard and Cerro Gordo counties. However, it is 

 not infrequent along highways and fields in many other parts of 

 the state. 



Fig. 201. Artichoke (Helianthus tuberosus). Common in corn fields, road- 

 sides, etc., north Iowa. 

 (Photographed by Colburn.) 



