38 Elementary Principles of Agriculture 



nourish the roots, hence the trees often die early in 

 the following spring. Sometimes a severe drought pre- 

 vents the trees from forming sufficient food, or insects, 

 fungous diseases, or storms destroy all the leaves. All 

 the reserve food is used up in an effort to form new 

 leaves, and the roots die of starvation. Transplanted 

 trees that fail to make a good growth often die at the 

 beginning of the second spring, because of the exhaustion 

 of their reserve food. 



62. Perennial Weeds and sprouts from stumps may 

 be killed by constantly destroying all leaf growth. Even 

 though it does not kill them completely the first season, 

 it may weaken them to such an extent that they may 

 be more easily killed by other means. If allowed to 

 grow to considerable size, the roots will receive food 

 materials sufficient to start vigorous new growth. 



63. Grasses and Weeds, like Johnson grass, that 

 form thick rootstocks are difficult to destroy. They 

 may be killed much more easily if they are kept grazed 

 down, so that the leaves do not have a chance to form 

 a store of reserve food for rootstocks. The half- 

 starved rootstock is much more easily killed than the 

 fully nourished one. Roots and other parts of plants, 

 when poorly nourished, are more easily killed by ex- 

 posure to cold, heat or drought. Hence, if such root- 

 stocks are prevented from forming leaves they may 

 die more quickly when exposed by plowing. 



63a. Make a list of the common weeds found in the fields, 

 orchards and gardens, in the community. Make a classified list, 

 putting all that come up from seed and mature a crop of seeds 

 before the middle of the summer [spring annuals] in one column ; 

 all that do not form seeds until late summer or fall [annuals] in a 

 second column ; and in a third column name all that live over win- 

 ter by underground roots, stems or root-stocks. 



