WEEDS AND WEED CONTROL 255 



DESTRUCTION OF WEEDS 



The destruction of weeds may be accomplished in a number of ways. 

 All of these are based on a scientific study of the vitality, morphological 

 structure and growth of the common weeds of farm and garden. The 

 following are the approved methods of controlling and exterminating 

 weeds. 



1. It is important to prevent the production of seeds in the attempt to 

 control weeds. It has been shown that some weed seeds have great vitality. 

 De Candolle, who first carried on experiments along this line, showed this 

 is especially true of the seeds belonging to the families Leguminosce and 

 Mahacece. Becquerel later studied the vitality of seeds and he found 

 that of 550 species investigated by him that the age of the seeds varied 

 from 125 to 1*35 years and that a few of the old seeds especially of the pulse 

 and mallow families germinated on trial. Ewart found that 6 per cent, 

 of the seeds of the common Indian mallow germinated after the lapse of 

 57 years and seeds of the white clover after 77 years and chicory after 

 10 years. The most noteworthy experiments were performed by Prof. 

 W. J. Beal of the Michigan Agricultural Experiment Station in testing the 

 vitality of seeds at intervals of five, ten, fifteen, twenty, twenty-five 

 years. The seeds were placed in sand in bottles slanting downward so 

 that water could not enter. These bottles were buried in the soil twenty 

 inches below the surface. The following seeds germinated on each of the 

 trials separated by five year intervals up to the twenty-fifth year. Ama- 

 ranthus retroflexus, Brassica nigra, Capsella bursa-pastoris, Lepidium vir- 

 ginicum, Anthemis cotula, Oenothera biennis, Polygonum hydro piper, 

 Portulaca oleracea, Rumex crispus. Stellaria media. Verbascum thapsus. 

 Success in exterminating weeds, where the seeds retain their vitality for 

 twenty-five years in the soil, is only the result of eternal vigilance in pre- 

 venting seed production. 



2. Weeds should be cut repeatedly, so as to exhaust the reserve sup- 

 plies of food stored in the underground parts. The underground parts 

 are thus starved to death. 



3. The soil should be cultivated intensively so as to root up and de- 

 stroy the growing weeds. 



4. The ground should be occupied by some cover crop which by the 

 density of its growth will crowd out the weeds. Larger heavier crops mean 

 fewer weeds. 



