24 



WEED FLORA OF IOWA 



Where these grasses are so abundant the ground becomes thickly 

 covered. Dr. Beal of the Michigan Agricultural College has found 

 that the seed retains its vitality for a considerable length of time. 

 After six years twenty-one seeds out of fifty germinated. The 

 seeds of all three species are much more tenacious when young than 

 when older. The ground is covered so thickly that only a few of 

 the plants are destroyed. Covering up with soil or exposing the 

 roots to the sun is effective. 



Fig. 11. A weedy cornfield : Foxtail, Sraartweed, etc. Such a weedy field ma- 

 terially decreases the yield of corn. Notice how the weeds have crowded 

 out the corn. 



(Photographed by Pammel.) 



Clark and Fletcher recommend as follows: "The only way to 

 eradicate this weed is to mow it or hoe it out before it goes to 

 seed. Anything which prevents it from going to seed for a number 

 of years will eradicate it in time. Most ground, however, is so full 

 of the seed that it takes a number of years of conscientious work to 

 exterminate it. 



