62 CLOVERS 



caused by the two cuttings, it sometimes proves ef- 

 fective in completely eradicating for the time being 

 this class of weeds. 



Distribution — Medium red dover is thought to 

 be native to Europe. It was probably introduced 

 into England some time early in the seventeenth 

 century. That it was attracting attention about the 

 middle of the century or a little later, is rendered 

 probable by the fact that it is discussed at consid- 

 erable length in the third edition of Blyth's "Im- 

 prover Improved," published in 1662, while it is 

 not mentioned in the first edition, published in 1650. 

 It was doubtless introduced into the United States 

 by the early colonists and at sundry times. 



Medium red clover will grow in good form only 

 in the temperate zone, since it cannot stand excessive 

 heat or excessive cold. The northerly limit of its 

 successful growth in North America is somewhere 

 about 50° north lati ude on the wind-swept prairies, 

 but on suitable soils, and protected somewhat by 

 trees and winter snows, it will probably grow 

 10 degrees further to the north. In British Colum- 

 bia, on the Pacific slope, it will probably grow as 

 far north as Alaska. But on prairies eastward from 

 the Rocky Mountains, it has not been grown with 

 much success much further north than 48°, unless 

 under the eastern shadow of the Rocky Mountains, 

 Low temperatures in winter, where there is only a 

 moderate covering of snow, are far less fatal 'o 

 clover plants than exposure to the sweep of the cold 

 winds. Even where the thermometer is not so low 

 as in the areas just referred to, such winds are par- 



