508 FIELD CROPS 



Canada thistle, dandelion, and other more persistent weeds, 

 unless the treatment is repeated several times. Clover and 

 alfalfa are injured more or less by any chemical spray. 



701. Weeds in Meadows. As in grain fields, prevention 

 is more effective than after treatment in dealing with weeds 

 in meadows. The land should be in good condition when the 

 seed is sown, and the seed itself should be free from weed 

 seeds. Clipping the field in the fall after the land has been 

 seeded to grass Avill prevent many weeds from seeding. The 

 seeding of weeds in older meadows may often be prevented 

 by cutting the hay crop a little earlier than would otherwise 

 be done. Such weeds as burdock, bull thistle, and mullein 

 may be exterminated by cutting them off below the crown 

 before they produce seed. Breaking up the meadow and 

 practicing a rotation of crops may be the only effective 

 means of eradicating some perennial weeds. The most com- 

 mon weeds of meadows are morning-glory, milkweed, dock, 

 sheep sorrel, toadflax, ox-eye daisy, the plantains, orange 

 hawkweed, Canada and other thistles, and quack grass. 



702. Weeds in Pastures. In pastures, the methods of 

 eradicating weeds are much the same as in meadows. Per- 

 sistent weeds may make it necessary to break up the pasture 

 and grow a cultivated crop. Where it is not practicable to 

 do so, repeated mowings when in blossom or cutting biennial 

 and perennial weeds below the surface of the ground will 

 eventually weaken them and prevent their spread. Sheep 

 render great assistance in keeping down weeds in pavStures. 

 Among the more common pasture weeds in different sections 

 of the country are squirreltail grass, or wild barley, broom 

 sedge, blue vervain, sheep sorrel, Russian thistle, milkweed, 

 mullein, yarrow, and Canada, bull, and sow thistles. 



703. Roadside Weeds. The weeds of roadsides are usu- 

 ally much the same as those of meadows and pastures, though 

 on new grading annual weeds are likely to make a rank 

 growth. Mowing two or three times during the season to 



