red three-awn

LC - Least Concern

NNR - Unranked

S3 - Vulnerable

Special Concern

Red three-awn is a medium-sized, slender, tufted, warm season 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 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 1⁄32″ to 1⁄16″ (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 1⁄64″ (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 5⁄16″ to ½″ (8 to 12 mm) long, the upper glume is ⅝″ 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 ⅝″ (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. There are usually some spikelets remaining on the plant through the winter.

4″ to 20″ (10 to 50 cm)

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

Mid-June through July

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

Sources

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

Native

Uncommon in Minnesota

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.

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.

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.