WHEATGRASSES 



Agropy'ron spp. 



The wheatgrasses form a genus of about 35 species widely dis- 

 tributed in temperate climates. Approximately two-thirds of these 

 species occur in the Western States, with Colorado apparently their 

 center of distribution. Wheatgrasses are erect perennials belonging 

 to the barley tribe (Hordeae), a tribe of the greatest economic 

 importance, as it includes such grains as wheat, rye, and barley, 

 as well as many highly important range and meadow plants. 



The wheatgrasses rank very high as range plants, especially in 

 the western United States where they are widely distributed and 

 often abundant. In general, sheep prefer the herbage of these 

 grasses while the plants are still young and succulent, but also 

 eagerly devour the seed heads of the unbearded or short-awned 

 species. Practically all species are continuously palatable to cattle 

 and horses and make excellent winter forage. In the Southwest, 

 the wheatgrasses when young and tender are grazed slightly by 

 deer, but when mature are spurned by these game animals. This 

 probably holds true in other parts of the country. Elk graze the 

 wheatgrasses to a somewhat greater degree than deer; buffalo or 

 bison prefer certain species, usually bluebunch wheatgrass (A. 

 spieatwm) , as winter forage. Slender wheatgrass (A. pauciflorum) , a 

 native species extensively grown as a hay crop, appears to have been 

 the first native American grass to be cultivated. Crested wheatgrass 

 (A. cristatum) introduced from Siberia, shows promise for re vege- 

 tating depleted range lands in the cooler portions of the mountain 

 and Great Plains States. 



For many years botanists considered the wheatgrasses and wheat 

 (Triticwm) as belonging to the same genus, and the older species 

 of Agropyron were originally placed under Triticwn. No doubt 

 the common name, wheatgrass, was applied because of the resem- 

 blance of many of the agropyrons to wheat. The scientific name 

 (from Greek, agros, a field, and pyfros, wheat) is another reminder 

 of this close resemblance and relationship. 



The heads (spikes) of wheatgrasses are commonly rather dense, 

 erect, and either conspicuously bearded (awned), short-awned, or 

 without awns, in general resembling the heads of wheat. Individual 

 flower clusters (spikelets) are three- to many-flowered, without indi- 

 vidual stalks (sessile), solitary or rarely in pairs at each joint of 

 the somewhat zigzag axis (rachis) of the spike. The rachis, al- 

 though jointed, does not break apart at these joints save in a few 

 exceptional cases, and the lowest (2) spikelet bracts (glumes) re- 

 main attached to the stem after the seed falls. In the cases of 

 three western species, rock wheatgrass (A. saxicola), spreading 

 wheatgrass (A. scribnem), and Saunders wheatgrass (A. saimdersii, 

 syn. ElymMS saundersii), however, the rachis tardily disarticulates. 

 Such species show a transition toward the related squirreltails 

 (Sitamon spp.). Rock wheatgrass and Saunders wheatgrass are 

 also remarkable among wheatgrasses in that their spikelets often oc- 

 cur in pairs at the rachis joints and the glumes are somewhat bristle- 



