DESCRIPTIVE MANUAL 391 



the fork may not be necessary in some wet and soft soils. The ap- 

 plication of kerosene to the crown of the plant, in the centre of 

 the rosette of leaves, is recommended. Sulphate of ammonia or 

 sulphate of iron in excess is also recommended. A small table- 

 spoonful of salt applied in the morning of a hot day, when the soil 

 is dry, will Mil them. 



Annual Sow-thistle {Sonchus oleraceus L.). 



Description. — Annual, succulent herb with leafy, smooth stems, 

 and pale yellow flowers in corymbose or umbellate clusters ; leaves 

 of stem dentate, runcinate-pinnatifid, terminal with a large seg- 

 ment; heads numerous; blossoms in late summer and fall. 



Distribution. — This weed is common in fields and waste places 

 throughout North America, especially in the north. It is common 

 in Europe and also occurs in Mexico and South America. 



Extermination. — Sow thistle is easily exterminated by cultiva- 

 tion. It can also be exterminated by the use of iron sulphate at the 

 rate of 100 pounds to a barrel of water; where it is abundant it 

 may be necessary to make two or three applications. 



Clark and Fletcher recommend as follows: "Prevent them 

 from seeding in waste places by cleaning them up and seeding them 

 to permanent, vigorous grasses. This annual weed, with its rela- 

 tively small, pale yellow flowers, when compared with perennial 

 species is not diiScult to control by ordinary methods of cultivation 

 and alternation of crops. Sheep, if sufficient in numbers, will pre- 

 vent sow thistles from seeding in pasture lands." 



The Iowa Homestead says concerning its eradication: "We 

 have seen the sow thistle take complete possession of a soil, 

 growing so thickly that other crops were entirely choked out. Nec- 

 essarily the best way to destroy it is to cultivate freely. If it 

 makes its appearance in stubble ground we would advise plowing 

 as early as possible after harvest and the cultivation of surface at 

 intervals tJuring the late summer and fall in order to keep the 

 thistles below the ground. 



