ECONOMICS OF WEEDS 



61 



(3) Rootstocks or perennial roots may be starved to 

 death by preventing any development of green leaves or 

 other parts above ground. This may be effected by build- 

 ing straw stacks over small patches, by persistent, thorough 

 cultivation in fields, by the use of the hoe or spud in waste 

 places, and by salting the plants and turning sheep on in 

 permanent pastures. 



(4) The plants may usually be 

 smothered by dense sod-forming 

 grasses or by a crop like clover or 

 millet that will exclude the light. 



(5) Most rootstocks are readily I 

 destroyed by exposing them to 

 the direct action of the sun dur- 

 ing the summer drought, or to the 

 direct action of the frost in the 

 winter. In this way plowing, for 

 example, becomes effective. 



(6) Any cultivation that merely 

 breaks up .the rootstocks and 

 leaves them in the ground, especially during wet weather, 

 only multiplies the plant and is worse than useless, unless 

 the cultivation is continued so as to prevent the growth 

 above ground. Plowing and fitting corn ground in April 

 and May, and cultivating at intervals until the last of June, 

 then leaving the land uncultivated during the remainder of 

 the season, is one of the best methods that could be pur- 

 sued to encourage the growth of coUch-grass and many 

 other perennial weeds. 



Recent studies by Spillman and Gates have shown that 

 the rootstock grasses, like quack grass, Bermuda grass, and 

 Johnson grass, are readily killed out by allowing the fields 

 to become meadows and pastures, so that a dense sod will 



GiOI/DENROD SEEDHEADS 



