Rothrock grama, also known as crowfoot grama and mesa grama, 

 is a relatively short-lived perennial with a meager root system, com- 

 monly forming small tufts 1 to 3 inches in diameter. Its specific 

 name commemorates Dr. Joseph Trimble Rothrock (1839-1923), an 

 eminent botanist, explorer, and conservationist known as the Father 

 of Pennsylvania Forestry. Rothrock grama occurs from southern 

 Utah through Arizona and southern California into Mexico, but is 

 of major importance in southern Arizona where it grows on the 

 mesas and gentle open slopes of the foothills. Its mam elevational 

 range is between 1,800 and 5,500 feet, but it is occasionally found at 

 either higher or lower elevations. At the lower altitudinal range 

 this grass grows chiefly on the deeper soils and more moist situations, 

 but at the upper elevations where more precipitation occurs it ex- 

 tends out over mesas and foothills in a wide variety of soils, vary- 

 ing from adobe to coarse gravelly or rocky sites. This species some- 

 times occurs in almost pure stands over large areas. It frequently 

 grows in mixture with black grama (Bouteloua eriopoda), needle 

 grama (B. ari^tidoides) , side-oats grama (B. cm-tip endula) , Hilaria 

 spp., desert hackberry (Ueltis reticulata) , mesquites (Prosopis spp.), 

 and catclaw (Acacia ^eggii). 



The great abundance of Rothrock grama makes it an outstanding 

 grass on some ranges. It varies from fair to good or even very 

 good in palatability during the growing season but rates somewhat 

 lower at other seasons of the year. This grass is highest in palat- 

 ability and of maximum forage value during the summer growing 

 season because it dries up quickly in the fall and does not cure as 

 well on the range as do other common gramas. Rothrock grama, 

 in contrast to most gramas, is a second-rate forage grass. Being 

 short-lived and poorly rooted, it does not withstand heavy grazing 

 satisfactorily, and rates as a so-called flash species, appearing or re- 

 ceding in accordance with climatic fluctuations. This characteristic 

 behavior explains why Rothrock grama is sometimes mistaken for 

 an annual grass. It decreases very noticeably during continued 

 drought but, being a prolific seeder, reappears rapidly under favor- 

 able conditions. 1 Rothrock grama is sometimes cut for hay, yielding 

 from 600 to 1,500 pounds an acre in favorable years on limited 

 areas where it is particularly abundant. The early pioneers of 

 southern Arizona are said to have used it rather extensively as hay. 



The species bears a family resemblance to blue grama (B. gracilis), 

 with which it is sometimes confused, although readily distinguish- 

 able from blue grama because of its growth in small bunches, rather 

 than in turflike patches, and by its more numerous (from 4 to 12; 

 commonly 4 to 6 on each stem) and somewhat finer flower spikes. 

 These spikes frequently lend a reddish brown tint to the landscape, 

 blending beautifully with the green of the open savanna wood- 

 land. The numerous slender leaves on the lower portion of the 

 stems usually give the plant a leafy appearance, which also helps 

 to distinguish it from blue grama. 



1 Thornber. J. J. THE GRAZING RANGES OF ARIZONA. Ariz. Aer. Ext. Sta. Bull. 65: 

 [245]-360, illus. 1910. 



