80 A TEXT-BOOK OF GRASSES 



the water-requirement. It also affects directly the growth 

 of crops. There is an optimum temperature for each 

 crop at which it thrives best. The temperature through 

 the growing season is of the most importance, though for 

 perennials the minimum winter temperature may be a 

 limiting factor. 



110. The timothy area. — This area extends from New 

 England to the southern boundary of Virginia and farther 

 south in the mountains and west to Minnesota and east- 

 ern Kansas, approximately to the 96th meridian. In 

 general this is the humid area. The rainfall is sufficient 

 on the average for the growing, without irrigation, of 

 the common meadow- and pasture-grasses, timothy 

 and blue -grass, and the legume, red clover. The 

 rainfall is distributed through the summer or growing 

 season. 



There are other humid regions in the United States 

 in the mountains of the western portion, isolated areas 

 where the rainfall is sufficient and the altitude not too 

 great. Timothy can be raised in Colorado up to about 

 9,000 or even 10,000 feet altitude. At higher latitudes 

 the altitudinal limit is lower. The most important humid 

 region of the West is the upper Pacific coast region lying 

 west of the Cascades and extending from Puget Sound 

 south into northern California. This differs from the 

 eastern humid region in having cooler summers and milder 

 winters with considerable rainfall. This region is emi- 

 nently adapted to pasture crops because of the mild, moist 

 winters. It is not so well adapted to hay crops because 

 of the difficulty of curing hay in the moist climate. (See 

 Farmers' Bulletin No. 271.) 



In the northern part of the timothy area, the Canada 

 field pea is much used (Par. 67). In the eastern part along 



