340 



WEED FLORA OP IOWA 



Fig. 197-A. Distribution of Black-eyed Susan. 



petioled and spatulate; heads many-flowered, radiate, neutral; 

 receptacle columnar or conical; chaff hairy at tip, acutish; ray 

 flowers yellow, disk dull brown; achenes 4-angled; pappus none. 



Distribution. — This weed is indigenous to the northern Missis- 

 sippi valley but has been naturalized eastward ; is common through- 

 out the state of Iowa, occuring not only in meadows but in some- 

 what sandy fields in Linn and Muscatine counties. 



Extermination. — This weed succumbs to cultivation but care 

 should be used in the sowing of clover seed as seed of this weed 

 is sometimes found with it. It is largely in this way that it has 

 been spread in the east. 



Common Sunflower (Helianthus annuus L.). 



Description. — A tall, rough annual, 6-8 ft. high, leaves 3-ribbed, 

 ovate or the lower cordate, serrate ; large heads with yellow ray 

 flowers, disk flowers brownish. 



Distribution. — Widely distributed west of Missouri river from 

 Saskatchewan to Texas, California and Mexico. Common in west- 

 ern Iowa, from Woodbury to Fremont county, occurring in fields 

 along highways, meadows, vacant lots and corn fields ; widely scat- 

 tered, but not abundant in many other sections of the state, as 

 Boone, Story, Polk, Cerro Gordo, Webster, Lyon, Linn and Mus- 

 catine counties. 



Extermination. — The seeds of this plant do not retain their vi- 

 tality very long. The young plants are easily destroyed by cultiva- 

 tion. The plant should not be permitted to go to seed. 



