14 FARM WEEDS OF CANADA 



Annuals may be eradicated from land, however badly 

 infested it may be, through any method by wtoich germination 

 is hastened and the young plants destroyed before they produce 



Biennials must be either plowed or cut down before they 

 flower. Mowing at short intervals in the second year, so as to 

 prevent the development of new seeds, will clear the land of 

 this class of plants; but a single mowing will only induce them 

 to send out later branches, which, if not cut, will mature many 

 seeds. Where plowing is impracticable, such plants should 

 be cut off below the crown of the root. 



Perennials are by far the most troublesome of all weeds 

 and require thorough treatment, in some instances the culti- 

 vation of special crops, to insure their eradication. Imperfect 

 treatment, such as a single plowing, often does more harm than 

 good, by breaking up the rootstocks and stimulating growth. 



For shallow-rooted perennials, infested land should be 

 plowed so lightly that the roots are exposed to the sun to dry 

 up. For deep-rooted perennials, on the other hand, plowing 

 should be as deep as conveniently possible. The nature of the 

 land must determine the depth of plowing. In light or gravelly 

 soils shallow plowing may be preferable as deep plowing might 

 interfere with the mechanical texture of the soil, which is so 

 important in the storing of moisture. 



The rootstocks of some perennial weeds are very persistent. 

 Small sections or cuttings from them will quickly take root 

 when they are distributed by plowing or cultivation. Where 

 such persistent perennials have become well established, it is 

 usually advisable to adopt the* most convenient method of 

 cultivation that will bring the rootstocks to the surface. They 

 should then be gathered and burnt or otherwise destroyed. 

 Most perennial weeds will, however, succumb to continued 

 thorough cultivation that will prevent the growth of leaves. 



Plants take in most of their food through their leaves. 

 Perennial plants, which live for many years, have special reser- 



