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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RED THREEAWN
Aristida purpurea Nutt. var. longiseta (Steud.) Vasey


Description

Growth habit: Perennial bunchgrass, 6 to 15 inches tall, growing in thick clumps.
Color: Green, curing to a tan. Old leaves from the year before usually give the growing plant a grayish green color.
Leaves: Short, rather stiff and inrolled.
Inflorescence: Seed stalks are usually short and branched. The scales surrounding each seed bear three awns, 2 to 3 inches long, spreading out at right angles from the tip of the spikelet. The awns are red when immature.
Season: Warm Season
Origin: Native

 


Figure 6.—Red threeawn (Aristida purpurea var. lonquiseta), plant and spikelet.

 

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Occurrence

Rather widespread and locally abundant in all counties except Maricopa, Yuma, and Santa Cruz, between elevations of 3,000 and 6,000 feet. It is most common on sandy or gravelly plains and hills but becomes established on better areas when the more palatable grasses are grazed out.

 

Forage Value

Red threeawn has a low palatability rating. Because of its abundance in some areas, however, it furnishes rather large amounts of forage, particularly from late July to early September. Growth begins late in the spring but little feed is produced until the summer rains begin. During the fall and winter when the plants are dry it has very little forage value.


Grazing Management

Red threeawn is much less palatable than blue grama or the other grasses with which it is commonly associated. As a consequence, it increases on heavily grazed ranges at the expense of the better forage plants. Although often an indicator of range deterioration, red threeawn may indicate only that the site is arid and has a well-drained soil.

Deep soils which support an abundance of red threeawn can be improved by light grazing, temporary nonuse, or winter only grazing.


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