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. Killing Johnson Grass. Grasses and weeds 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. 



64. The Storage of Reserve Food. Annual plants use 

 their food supplies as fast as formed, in developing the 

 shoots and roots, and, particularly, in forming flowers 

 and fruits. Some plants, like turnips, cabbage, radish, 

 etc., store the surplus food in the stem, leaves or roots 

 during the first season, and use it during the next season 

 to nourish a large crop of seeds. If grown in warm cli- 

 mates, these plants will complete the cycle in one sea- 

 son. In plants that live from year to year (perennials), 

 food is stored up in the stems and roots, to supply the 



