DESCRIPTIVE MANUAL 



93 



Fig. 52. 



Common Smartweed or Water Pepper (Polygonum hydropiper) . 

 (Photographed by Colburn.) 



Lady's Thumb (Polygonum persicaria L.). 



Description.— A nodding, smooth, glabrous annual; sheaths 

 bristly ciliate; leaves lanceolate, marked with a conspicuous dark 

 or lunar spot ; spikes short cylindric ; peduncles smooth ; achene flat- 

 tened, smooth and shining. 



Distribution. — Lady's thumb is native to Europe, common in east- 

 ern North America, Rocky mountains and on the Pacific coast. 

 Common everywhere in Iowa, particularly in waste places and gar- 

 dens, and growing up abundantly after grain has been harvested. 



Extermination. — This weed is easily destroyed by cultivation. 

 The main point, however, is that seed production must be prevented ; 

 hence it would be well to cut off the plants after they have started 

 to produce flowers ; this will effectually prevent seed production. 



