DESCRIPTIVE MANUAL 



97 



Fig. 54-C. Distribution of "Water Smartweed. 



Extermination. — Since this perennial weed is most abundant in 

 sloughs, drainage must be resorted to before an effective means of 

 extermination can be used. After this it will give little trouble in 

 cultivation. 



The Water Smartweed {Polygonum acre H B K) is a nearly 

 smooth perennial with stems rooting at the decumbent base; erect, 

 dense spikes of whitish or flesh-colored flowers. It is common in 

 low grounds. 



Black Bindweed or Wild Buckwheat {Polygonum convolvulvs L.). 



Description. — An annual, twining, with smooth joints; leaves 

 halberd or heart-shaped ; flowers in corymbose racemes ; achene dull 

 black, triangular and minutely roughened. 



Distribution. — This weed is widely scattered with grain seed, 

 especially with wheat and oats. It is often most troublesome in 

 small grain fields. In Iowa, however, it occurs in gardens and along 

 roadsides. 



Extermination. — It is not difficult to destroy the weed by giving 

 clean cultivation, since it succumbs easily to such treatmen-t. Sow 

 only clean seed. 



Clark and Fletcher recommend as follows: "Sow clean seed 

 grain. The seeds retain their vitality for a relatively short period, 

 probably not longer than three years, except in the drier soils of the 

 western plains. The suppression of this pest is therefore largely 

 dependent on the prevention of a continued supply of fresh seeds to 

 the soil. This weed gives little trouble on land under a short rota- 

 tion of crops, including hay, for two years. 

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