Arizona Range Grasses
Their Description, Forage Value, and Grazing Management
Cooperative Extension,College of Agriculture & Life Sciences, The University of Arizona

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PURPLE THREEAWN
Aristida purpurea Nutt. var. purpurea

Description

Growth habit: Perennial bunchgrass in small dense clumps, 1 to 2 feet tall.
Color: Dark green curing to gray or straw color. In seed, the awns give the plant a purple color.
Leaves: Three to 6 inches long, small, firm, inrolled.
Inflorescence: Open with slender branches that curve or droop with the weight of the seed. Spikelets have three awns that are shorter and less divergent than those of red threeawn.
Season: Warm Season
Origin: Native

Figure 7.—Purple threeawn (Aristida purpurea var. purpurea), plant and spikelet.   View Larger Image Click Here

Occurrence

In all counties of Arizona except Navajo, Coconino, Greenlee, and Yuma. It generally grows on rocky or sandy plains and slopes at elevations between 1,000 and 5,000 feet. In the lower portion of its range it is very common along roadsides.

Forage Value

One of the poorest forages of our common range grasses. Palatability is low, particularly after the plants are mature.

Grazing Management

Purple threeawn should be grazed while growing most actively. Because the plants green up in the spring more than many southwestern grasses, they can usually be grazed to advantage in March and April. Maximum growth occurs in the summer, and ranges with an abundance of this grass will be most productive after the onset of the summer rains.
Like red threeawn, this grass often indicates past range misuse, tending to replace the better grasses under heavy grazing. Light use, temporary nonuse, or winter grazing of these areas will give other grasses a chance to increase.

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Document located http://cals.arizona.edu/pubs/natresources/az1272/
published 2002
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