ERADICATION OF WE ED 8 



503 



a few weeks later. The frequent use of the cultivator helps 

 to keep down annual and other weeds in cultivated fields. 

 Various methods of preventing annual weeds from producing 

 seed are suggested in the paragraphs which follow on the 

 treatment of weeds in special crops. 



696. Biennial Weeds. 

 Biennial weeds are nei- 

 ther as numerous nor as 

 difficult to eradicate as 

 the annuals with their 

 great powers of seed pro- 

 duction, or the perennials 

 with their persistent 

 roots. Cutting off the 

 plants below the crown 

 during the first year or at 

 any time in the second 

 before the flowers are 

 produced will kill bien- 

 nial weeds. Biennial weeds are seldom troublesome in cul- 

 tivated fields, for they are usually destroyed by plowing. 

 In other locations, the quickest and easiest method is to cut 

 off the plants below the surface of the ground with a small 

 spade. 



697. Perennial Weeds. Cultivation is the most efficient 

 means of destroying perennial weeds. Smothering the roots 

 by preventing them from producing leaves, by frequent cul- 

 tivation, by covering with straw or other material, or by 

 sowing with some quick-growing crop like rape or sorghum, 

 is often successful. One of the best ways of eradicating per- 

 sistent perennials is to plow them under about the time the 

 plants are coming into bloom and to cultivate the land so 

 thoroughly during the rest of the season with the disk or 

 spike-tooth harrow as to prevent them from producing leaves. 

 The next season the land may be put into a cultivated crop 



rigure 162. — Squirreltail. 



