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WEED FLORA OP IOWA 



Fig. 81-A. Distribution of Pennycress. 



base ; root leaves petioled ; flowers white ; petals nearly equal ; seeds 

 purplish brown, longer than broad; cotyledons accumbent. 



Distribution. — CJommon in waste places, particularly in clover 

 fields; Story, Woodbury, Winneshiek, Allamakee and some other 

 counties in the state. Common in Manitoba, Minnesota, Dakota, and 

 eastern Canada, particularly in the prairie provinces. The weed 

 is abundantly distributed by spring floods and also to some extent 

 by clover seed. 



Large Peppergrass {Lepidium virgiiucum L.). 



Description. — ^An erect annual, at first quite simple, later much 

 branched, 8 in.-2 ft. high ; leaves divided, entire or vrith irregular, 

 pointed teeth ; flowers small, white ; pod circular or oval with a lit- 

 tle notch at the upper end; seeds light brown, elongated, with a 

 prominent ridge on one side, on addition of water becoming muci- 

 laginous; cotyledons accumbent. 



Distribution. — ^Large peppergrass is native to the Mississippi val- 

 ley, east to New England; more common in Missouri, Illinois and 

 Ohio. It is widely scattered in Iowa, being particularly common 

 in timothy meadows in some years. 



Extermination. — This peppergrass sometimes comes up abund- 

 antly in the fall. The fields should, therefore, be plowed in the fall 

 and when sowing small grain given a thorough dragging. In com 

 fields the ordinary methods of cultivation will destroy the weed. 

 Do not permit any of the plants to seed. Frequent in timothy seed. 

 Sow only clean timothy seed. 



