82 



WEED FLORA OF IOWA 



Fig. 45-A. Distribution of Sheep Sorrel. 



Chemical Composition. — The ash of this weed is reported by Wein- 

 hold as follows : 



Erect Knotweed {Polygonum erectumh.). 



Description. — An annual, glabrous, stout, erect, or ascending yel- 

 lowish green herb, 1-2 ft. high, with elliptical leaves ; flowers yellow- 

 ish and inconspicuous, 1-2 in an axil; stamens 5-6; achene dull, 

 included. 



Distribution. — Widely distributed from the northeast to Mani- 

 toba, Wisconsin, Minnesota to Arkansas, and eastward. , Common 

 in Iowa especially eastward, and in Story, Boone, Marshall, Polk, 

 Allamakee, Clinton and Dubuque counties; 



Extermination. — Easily exterminated by cultivation. 



