Weeds 



1753 



fields destroy them by mowing dose, piling on other litter and 

 burning the spots over, or by grubbing np the land. If it is well 

 distributed there is nothing to do but to plow up the land and seed 

 over again. If all old plants on the soil are destroyed it is not 

 likely that dodder will reappear unless seed is again introduced. 

 Among biennials there are numerous noxious weeds. Wild 

 carrot, wild lettuce, yellow daisy and burdock are common. 

 Biennials die after producing seed. If we cannot succeed 



Fig. 142. Good Homemade Device for Spraying Mustard and Other Weeds, or 



Potatoes 



in destroving them durinir their earlier stages of growth, 

 but can manage to prevent the seed produced from reaching 

 the soil, we shall accomplish much. Unfortunately some bi- 

 ennials if prevented from producing seed at the usual period 

 do not die but persist season after season in the attempt to pro- 

 duce seed. The burdock which normally dies at the end of the 

 second season, if not allowed to produce a seed stalk, as in case of 

 growing in a la\vn, will live for a dozen years. In case biennials 

 have become established the seed stalk should be permitted to de- 

 velop in order to exhaust the root, and then destroyed before the 

 seed becomes scattered. This is usually a difiicult task to accom- 



