166 AGRICULTURE ON THE PACIFIC SLOPE 



by poisons. In lawns gasoline is used; enough is 

 placed at the root of the weed to kill it. It soon evapo- 

 rates and does not injure the grass. Along the roads 

 and sidewalks arsenic or petroleum may be used. 

 They stay in the soil and prevent anything from growing 

 where they have been placed. A 15 per cent solution 

 of iron sulphate applied with a sprinkler often kills 

 weeds in a lawn or grain field without hurting the 

 grass. Poisons should never be handled by children. 



ANNUAL WEEDS 



Annual weeds are very easily got rid of, if they are 

 not allowed to go to seed. Not a single plant should 

 be allowed to blossom or set seed if it. can be helped. 

 The best time to kill them is when they are tiny seed- 

 lings. But many people do not recognize them at this 

 stage. For this reason pictures are given here of 

 several common weeds at an early stage of growth. It 

 is important to recognize and destroy all kinds of weeds 

 at this stage. 



Many farmers pay no attention to the little "summer 

 weeds/' because they are so small. But as they pro- 

 duce a great deal of seed it is very important to destroy 

 them. The little wheels of bur clover, knotweed, 

 Napa thistle, pigweed, and filaree, which lie close to the 

 ground and are hardly noticed in summer, cause a 

 great deal of trouble later on. 



