red three-awn

(Aristida purpurea var. longiseta)

Conservation Status
red three-awn
Photo by Nancy Falkum
  IUCN Red List

LC - Least Concern


NNR - Unranked

S3 - Vulnerable


Special Concern


Red three-awn is a medium-sized, slender, tufted, warm season (C4) grass. It occurs in the western half of the United States, in adjacent Canadian provinces, and in northern Mexico. It is uncommon in Minnesota, where it is at the easternmost extent of its range. It is found on dry and moderately dry (mesic) hillsides, open prairies, and rock outcrops. It is also found in disturbed areas, including roadsides, railroads, and abandoned fields. It grows under full sun in dense, often large tufts, in well-drained, fine-textured soils. It is drought tolerant but decreases in periods of extended drought. It is listed as a species of special concern in Minnesota due to habitat loss.

Red three-awn has a fibrous root system. It does not form underground horizontal stems (rhizomes).

The stems (culms) are hollow, hairless, round in cross section, and 4 to 20 (10 to 50 cm) tall. They may be erect or curve upward from the base (ascending). They are usually unbranched.

The leaves are usually mostly clustered at the base (basal). The base of the leaf that wraps around the stem (sheath) is open and hairless. It does not disintegrate into thread-like fibers at maturity. The blade is grayish-green and linear. It can be 1½ to 10 (4 to 25 cm) long but is usually no more than 4 (10 cm) in length. It may be flat and slightly curved, but it usually rolls inward on top, stands stiffly erect, and appears wiry. When unrolled it is 132 to 116 (1.0 to 1.5 mm) wide. The tip is sharply pointed. The upper surface is rough. The collar is inconspicuous. It does not have developed shoulders or ear-like projections (auricles). It often has a tuft of long hairs on each side.The ligule is tiny, just 164 (0.1 to 0.4 mm) in length. It consists of a fringe of short hairs on a short membranous base.

The inflorescence is a narrow, nodding, sparingly branched cluster (panicle) at the end of the culm. The panicle is 2 to 6 (5 to 15 cm) long. The branches are short and stout. They are stiff and appressed or curved upward at the base, delicate and drooping at the top.

The spikelets are reddish. This is the feature that gives the species its common name. Each spikelet has a single flower, a pair of sterile glumes, and a single fertile lemma. The lower glume is 516 to ½ (8 to 12 mm) long, the upper glume is to 1 (16 to 25 mm) long. The glumes are translucent and have a short, stiff, bristle-like extension (awn) at the tip. The lemma is ½ to (12 to 16 mm) long. The lemma has three long awns at the tip. This is the feature that gives the genus its common name. The lemma awns are nearly equal in length. They can be 1 to 4 (2.5 to 10 cm) long but are usually 1½ to 2¾ (4 to 7 cm) in length. This is the feature that gives the subspecies its scientific name. The awns are reddish, soft, and parallel to the stem at first. As the seed matures, the awns become pale and stiff, and spread widely, eventually at an angle of about 120° to each other. Some spikelets usually remain on the plant through winter.




4 to 20 (10 to 50 cm)


Similar Species


Dry. Hillsides, open prairies, rock outcrops, roadsides, railroads, and abandoned fields. Full sun. Well-drained, fine-textured soils.




Mid-June through July


Pests and Diseases






The sharp awns can cause injury to the eyes, nose, and mouth of livestock




Distribution Map



2, 3, 4, 5, 6, 7, 24, 28, 29, 30.








Uncommon in Minnesota

  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Liliopsida (monocots)  


Poales (grasses, sedges, cattails, and allies)  


Poaceae (grasses)  


Aristidoideae (threeawns, wiregrasses, and bushman grasses)  


Aristideae (threeawns, wiregrasses, and bushman grasses)  


Aristida (three-awn)  
  Species Aristida purpurea (purple three-awn)  

There are seven recognized varieties of Aristida purpurea. Only var. longiseta occurs in Minnesota.

Some authoritative sources, including Plants of the World Online (POWO) and World Flora Online, classify this as the species Aristida longiseta.


Subordinate Taxa






Aristida curtiseta

Aristida fasciculata var. nuttallii

Aristida longiseta

Aristida longiseta ssp. rariflora

Aristida longiseta var. longiseta

Aristida longiseta var. rariflora

Aristida longiseta var. robusta

Aristida pallens

Aristida purpurea ssp. robusta

Aristida purpurea var. robusta

Aristida rariflora


Common Names


dogtown grass

Fendler’s threeawn

Fendler threeawn

red threeawn

red three-awn

wire grass











Growing upward at an angle or curving upward from the base.



In grasses: The area on the back of a grass leaf at the junction of the sheath and the blade. On moths: the array of scales on the dorsal part of the prothorax.



The hollow or pithy stem of a grass, sedge, or rush.



A chaffy, empty, sterile bract at the base of a grass spikelet. Glumes usually occur in pairs, but occasionally only one is present.



The outer, lowermost of the pair of bracts at the base of the grass floret; it ensheathes the palea.



In grasses and sedges, a membranous appendage at the junction of the leaf and the leaf sheath, sometimes no more than a fringe of hairs. In flowering plants, the flat, strap-shaped, petal-like portion of the corolla of a ray floret.



Long, straight, and narrow, with more or less parallel sides, like a blade of grass.



A pyramidal inflorescence with a main stem and branches. Flowers on the lower, longer branches mature earlier than those on the shorter, upper ones.



A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.



The lower part of the leaf that surrounds the stem.


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Nancy Falkum


I am pretty sure this is Three Awn Grass before twisting. We did find some close by that was twisted, the photo did not show clearly.

  red three-awn  
    red three-awn   red three-awn  





Aristida purpurea var. longiseta - purple threeawn
Matt Lavin
  Aristida purpurea var. longiseta - purple threeawn  

Purple threeawn is a native perennial bunchgrass common in arid rangeland and mostly in disturbed settings, such as along roadsides. The inflorescence is a narrow panicle, the ligule is hairy, and the first glume is distinctly shorter than the second glume. The single floret per spikelet bears a tripartite awn from the tip of the lemma. This grass species is highly variable morphologically. The awns vary in length from about 1-3.5 cm in variety fendleriana (Fendler threeawn) or 3.5-14 cm long in variety longiseta (purple threeawn). The long awned form is common along roadsides form usually has straight green leaves borne from the stem. The short awned from is common on rocky substrates and outcrops and usually has curly leaves congested in a basal bunch. The two forms can co-exist. After the florets have dispersed, this species may be difficult to distinguish from species of the cool season genus Stipa because of spikelets with large thin-textured glumes that are arranged in a spicate panicle. Aristida has a conspicuously hairy ligule, unlike species of Stipa.




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Other Videos
  Aristida purpurea, (Purple three awn) Grass, graceful, wind dancing.
Koby's Garden Alchemy

Oct 20, 2019

This shimmering, purply-rosy display heralds the beginning of warm weather. After sun-bathing for months, it then matures into a veritable blonde beauty. There aren't many grasses that have the sublime tonal transformation of Aristida purpurea, commonly called "Purple three-awn". Aristida purpurea, by many accounts, seems to be a moderate seeder. It could be an alternative or replacement for the more aggressive seeding of "Mexican Feather Grass" / "Argentine needle-grass" - Nassella (Stipa) tenuissima. "Purple three-awn's" sinuous nature sways and sweeps with the breeze. It's vast N. American range, from Canada to Mexico and the minor water requirements, only add to it's ease and attraction . . .(find out more watching the video). This video is only an introduction. Nothing replaces on-site consultation from a professional. Yet, hopefully this will plant a seed that furthers curiosity and exploration of the wonders around us. Please click the like for my video and subscribe, this fuels future productions.

Koby's Garden Alchemy: Artistic Design, Fine Horticulture & Planters Perfected.




Visitor Sightings

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  Nancy Falkum

Location: Kellogg Weaver Dunes SNA, Weaver Dunes Unit

I am pretty sure this is Three Awn Grass before twisting. We did find some close by that was twisted, the photo did not show clearly.

red three-awn





Created: 11/17/2021

Last Updated:

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