90 WEED FLORA OF IOWA 



treating it is by thorough cultivation, exposing all the root-stocks 

 to the sun, then removing the young plants as rapidly as they makt 

 their appearance. 



Wallace's Farmer suggests the following treatment: "It grows 

 less vigorously on well drained land, hence the first step in eradica- 

 tion is to drain the field thoroughly. The summer fallow is perhaps 

 the best course of treatment. Plow the infested patch early and 

 keep the disk and plow working on it regularly all summer long. 

 All the roots that can be located should be pulled up and burned 

 after drying out. A heavy pitchfork and plenty of muscle will soon 

 fill a wagon box with the long, tough, yellow roots. A heavy seed- 

 ing of sorghum helps to weaken the stand, but we have seen patches 

 as vigorous as ever a year after two succeeding crops of sorghum 

 had been grown in an effort to smother out the pest. ' ' 



Smartweed (Polygonum pennsylvanicum L.). 



Description. — An annual 1-2 ft. high, with lanceolate leaves; 

 branches below the flowers beset with numerous stalked glands; 

 flowers whitish or rose-colored ; stamens 6-8, style 2-cleft ; fruit an 

 achene, 1% lines long, flattened, brown, shining, part of the calyx 

 remaining attached to the base. 



Distribution. — Pennsylvania smartweed is common from New 

 England southwestward and westward and in every part of Iowa, 

 coming up abundantly in corn fields, sometimes forming a mass of 

 rose-colored flowers; also growing up abundantly in grain fields 

 after harvest. 



Extermination. — This smartweed is easily exterminated by cul- 

 tivation. 



