Blue grama, also known locally as white, red, or purple grama, though not 

 quite as widely distributed as hairy and side-oats gramas, is, without doubt, 

 the most common species of grama throughout the Western States and economi- 

 cally the most important species of the genus. It occurs from Wisconsin to 

 Alberta, California, and Texas, extending southward, through Mexico, into 

 South America. It is found in all the Western States except, possibly, Wash- 

 ington, Oregon, and Idaho, and is especially characteristic of the short grass 

 areas of the Great Plains. 



Blue grama varies considerably in growth habits and general appearance 

 in different parts of its range. In the northern part, and under favorable 

 moisture conditions, it tends to form a sod. Farther south on the Plains and 

 other places where conditions are less favorable as a result of less rainfall 

 or higher evaporation, it does not form so complete a cover but occurs in 

 patches, and along the Mexican border at an elevation of about 5,000 feet 

 it has more the appearance of a bunchgrass. 1 In the North the stems seldom 

 reach a height of over 12 to 16 inches, sometimes being as low as 6 inches, 

 but in the Southwest stems 2 to 2% feet high are not uncommon. 



Blue grama occurs on rather dry plains and foothills, as well asi in the 

 mountains in the woodland and ponderosa pine zones, inhabiting sandy or 

 gravelly soils and also compact loams and gumbos. It is a quick-growing 

 species and matures 1 in about 60 to 70 days. Growth ordinarily does not 

 start, or at least is very light, until after summer rains begin. The species 

 is drought-resistant and has the ability to become dormant during drought 

 periods in what would normally be the growing season. Subsequently, as 

 soon as moisture becomes available, if temperatures are sufficient, it greens 

 up and immediately resumes growth. 



Generally, blue grama is rated as a choice forage species for all classes of 

 livestock. It withstands grazing very well. On ranges suitable for fall and 

 winter grazing it does best and yields greatest returns if it is grazed lightly 

 in the summer during the period of rapid growth and is allowed to mature a 

 crop, which, curing well on the ground, makes very good fall and winter for- 

 age. It forms a fairly good ground cover which gives it great soil-protective 

 value. Its drawbacks as a range forage plant are that, over much of its 

 range, it produces a relatively small crop and practically no green forage 

 during spring and early summer at the time when succulent forage is espe- 

 cially desirable. However, it is a valuable forage plant for use at any time 

 in the Southwest, where the spring growth of grasses is normally scanty. 



Blue grama roots appear mainly in the upper 18 inches of soil, most of the 

 roots being near the surface ; consequently the grass is well adapted to situa- 

 tions where, because of a compact soil through which water percolates slowly, 

 or because of light storms, much of the moisture during the growing season 

 is confined to the surface 6 or 8 inches of soil. Under these conditions blue 

 grama, and perhaps some of the other gramas also, forms the climax vegeta- 

 tive type. On many ranges, however, the grama or short grass type has come 

 in as a result of heavy grazing, which has helped to eliminate the bunch 

 grasses or tall grass which naturally occupy such areas. Studies on the 

 Coconino Plateau by Hill and Talbot 2 show that blue grama, after long pro- 

 tection, gives way to some extent to the bunchgrasses where it is growing 

 near the upper elevational limits of its range but, on the open range, easily 

 holds its own under light grazing and withstands heavy grazing remarkably 

 well. Even though grazing of this species by domestic livestock is care- 

 fully regulated, it is often subject to severe use by rodents. The seed habits 

 of blue grama are weak and probably only in favorable years is a crop of 

 good seed produced. However, this is offset to a considerable extent by the 

 fact that the plants spread rather vigorously by tillering. 



Typically each slender, erect, smooth stem of blue grama bears two spikes, 

 but stems with one or three are not uncommon, and occasionally as many 

 as six spikes will be found on a stem. The numerous leaves are mostly 

 basal, from 1 to 4 inches long, rather narrow, flat, and smooth, and bear a 

 few soft, white hairs t the junction of blade and sheath. The specific name 

 ffracilis refers to the slender, graceful habit of this species. 



1 Griffiths, D. TUB GRAMA GRASSES : BODTELOUA AND RELATED GENERA. U. S. Natl. Mus., 

 Contrib. U. S. Natl. Herbarium 14 : 34-3-444, illus. 1M2. 



2 Talbot, M. W., and Hill, R. R. PROGRESS REPORT ON RANGE STUDY PLOTS, COCONINO 

 NATIONAL FOREST. 33 pp. 1923. [Unpublished ms.] 



