WEEDS AND THEIR ERADICATION 355 



consideration for purchase. If the farmer cannot determine with reasonable 

 certainty as to their purity and germinating power, he should submit his 

 sample to the experiment station of his state, that the weed seeds may be 

 identified. These institutions gladly test samples of seeds for farmers free 

 of charge. 



Careful screening will overcome much of the difficulty with weed seeds. 



Classification of Weeds. — It is not enough to know the name of a 

 weed. In order to win in the struggle against a weed enemy, one must 

 know its habits of life and its methods of propagation. There is no weed so 

 vicious that it cannot be subdued or even entirely eradicated if its habits 

 are understood. 



Weeds may be divided into three classes according to their life cycle: 

 annuals, biennials and perennials. Annuals complete their growth and 

 ripen seed in one season, such as wild mustard and ragweed. These weeds 

 must depend upon seed in order to grow again the following year. It can 

 readily be seen that if the plant is destroyed before seeds form, the source 

 of next year's crop is much lessened. 



Unfortunately, some of these seeds are encased in an oily covering, 

 enabling them to resist decay. Wild mustard seed, for instance, has such 

 power of vitality that it has been known to germinate after having lain in 

 the ground for many years. 



Biennials are not so easily disposed of. They require two years in 

 which to complete their growth. Some of them have long tap roots in 

 which they store up plant food during the first year. This food is used to 

 produce seed during the second summer. Burdock and wild carrot are 

 common examples of this class. These weeds are seldom seen in cultivated 

 fields, for the 'plow and cultivator are disastrous to their roots. If these 

 weeds are cut off even with the ground, they branch out and become 

 thicker than before. Cutting two or three inches below the surface so as 

 to destroy the crown of the plant is effective. 



Perennials grow year after year and produce seed indefinitely. Some 

 of them reproduce by seed only, such as the ox-eye daisy and dandelion. 

 Others have roots running under ground from which they send up new 

 plants yearly. Common examples of this kind of weed are Canada thistle 

 and bindweed. This class of weeds is the most difficult to eradicate, 

 for wherever these roots are cut or bruised new stalks are sent forth 

 and the difficulty increased. There is one time, however, during the 

 growing season when these weeds are most effectively attacked; that is, 

 when they are in full growth, but before seeds form. No plant can live 

 long without a leaf system. If the plants are cut off and plowed under at 

 this time, many of them will be eradicated. 



Repeated and persistent attacks, however, on the part of the farmer 

 will be necessary for ultimate success. The poorer the land becomes, the 

 greater the number of biennial and perennial weeds. They seem to be best 

 adapted to the poor conditions and will thrive where other crops fail. 



