224 ECONOMIC PLANTS 



grown to such an extent that it should not be allowed 

 to occupy the land continuously, except upon reclaimed 

 swamp lands, where it may be grown years in succes- 

 sion. It is propagated by rootstocks (see page 154) set 

 a few inches apart in shallow trenches 30 inches apart. 

 It must be kept perfectly free from weeds, first by 

 horse cultivation, then by hand. In midsummer the 

 tops are cut and cured like hay, then stored under 

 cover for distilling. In this country mints are raised 

 most extensively in southwestern Michigan and north- 

 western Indiana. 



GRASSES 



Grass Crop. All the grasses and clovers that are 

 used for pasturage and hay are known by the general 

 term grass crop. In spite of the fact that the corn and 

 wheat crops show a greater cash value, the grass crop 

 is really the most valuable and the most important 

 crop grown. The estimated cash value of the hay crop 

 does not include the worth of the pasturage, of which 

 there is an immense area in the United States. The 

 production cost of the corn crop is much greater than 

 that of hay, so that the net profits from the two crops 

 are approximately equal. Again, the full value of hay 

 to the farmer does not appear in the statistical figures 

 of the value of the crop. The grasses, while being 

 grown for hay, store the ground with humus by the 

 decay of their roots and stubble, and forage plants rich 

 in nitrogen, like the clovers, leave nitrogen, the most 

 costly fertilizer, in the soil for the succeeding crop in 

 the rotation. The indirect value of the grass crop to 

 the farmer fully equals the direct cash value of the hay. 



Professor Thomas Shaw says : " In the absence of 

 grass, the humus supply in the land cannot be so well 



