406 THE CLOVERS 



Clover sickness is a term usually applied to the soil when clover 

 can no longer be grown on land where it previously grew. The 

 causes of clover sickness are not well known, but it has been demon- 

 strated that one cause is the decreasing lime content of the soil. On 

 many such soils the addition of lime has restored clover growing. 

 It is claimed, however, to fail even where lime is added. 



Inoculation for Clover. In general, artificial inoculation has 

 not been practised. It is probable that more or less natural inocula- 

 tion is carried about on clover seed and probably in this way it was 

 first distributed throughout the country. Red clover is so ex- 

 tensively grown that it has usually not been necessary to inoculate. 

 However, in new regions, it is sometimes difficult to secure stands of 

 red clover for many years, and it is probable this is due to lack of 

 inoculation. Recent experiments have shown that in regions where 

 red clover has not been cultivated for many years inoculation usually 

 gives better results. 



ALSIKE CLOVER 



Alsike clover (Fig. 176) derives its name from the province of 

 the same name in Sweden, where it has long been extensively grown. 

 It seems to have been brought into cultivation probably in Sweden 

 or that vicinity. It is mentioned as a cultivated forage crop in 1750. 

 From there it spread to England and adjoining countries in Europe, 

 and was apparently introduced quite early into the United States, 

 though it does not seem to have been cultivated to 'any extent, at 

 least, until 1850. The early botanist Linnaeus thought it to be a 

 hybrid between red clover and white clover, but it is doubtful whether 

 this is the case. 



Characters. Alsike clover is a long-lived perennial, and in this 

 differs from red clover, which is a short-lived perennial. The stems 

 are about as tall as those of red clover, but are more slender and 

 prostrate at the base. It also differs from red clover in having a 

 more or less continuous growing season throughout the summer. 



Climate and Soil Adaptations. Alsike clover has a much 

 wider range of adaptation than red clover. It naturally prefers a 

 cool climate and wet soil ; but it will endure at least as much dry 



