A STUDY OF THE ROOT-SYSTEMS OF PRAIRIE 

 PLANTS OF SOUTHEASTERN WASHINGTON 



JOHN ERNST WEAVER 



University of Minnesota, Minneapolis, Minn. 



(Concluded) 

 II. 



Agropyron spicatum (including var. inerme) (Fig. 10) 



This is the most common bunchgrass in eastern Washington. 

 It has its best development westward of the high upland prairies 

 of extreme eastern Washington and along the rim-rock through 

 the eastern part. The bunches are often 10 inches in diameter 

 and reach a height of over 3 feet. As many as 300 to 350 

 individual stems may occur in a single bunch. The plant 

 blossoms in June and dries out in early July, only to take on 

 renewed growth after the autumn rains, and remain green all 

 winter. Figure 10 shows Agropyron on the rim-rock with its 

 roots penetrating the rock crevices to depths of 45, 46 and 48 

 inches. Ten plants were examined under these conditions. The 

 roots of all followed the cleavage planes of the basalt on an 

 average to a depth of 4 feet and 1.3 inches, but one extended 

 along the deeper moist crevices to a depth of 5 feet. 



In the well-developed highland prairies the bunch habit is 

 partially abandoned and long rhizomes are produced. The 

 clumps are always much smaller here, perhaps only a few centi- 

 meters wide, but there are usually as many as 5-6 per square 

 meter. Twelve prairie Agropyrons were examined. This grass 

 has coarser roots than any of the other three important native 

 grasses. These coarse, fibrous roots have many short laterals. 

 Some of these roots reach a depth of 4 feet and 9.5 inches, al- 

 though on an average 4 feet and 2 inches was the greatest depth 

 attained. Five plants on a southwest slope gave an average 

 depth of 4 feet and 1.6 inches, while seven on a northwest slope 

 reached an average depth of only 3 feet and 2.6 inches. 



273 



