Rough Bentgrass

Agrostis scabra
Species distinguishing characteristics: 
  • Forms dense tufts, 20–80 cm tall, of short, narrow leaves
  • Leaves, stems, and branches of flower clusters are rough to touch
  • Large, delicate, purplish flower cluster with widely spreading, hair-like branches and spikelets borne near branch tips
  • Spikelets have a single floret, equal-sized glumes, and lemmas without awns
  • Short, narrow leaves are mainly basal with a ragged, round tipped ligule
Family Characteristics: 
  • Flowering stems have nodes and are hollow and round in cross section
  • Alternate leaves sheath the stem on their lower portion and form a hairy or membranous scale (ligule) inside the base of the leaf sheath
  • Flower clusters of numerous spikelets attach directly to the flowering stem (spike) or attach by small stalks, and are often branched (panicle)
  • A pair of bracts, called glumes (the outer/lower one being larger), enclose spikelets at the base
  • Each spikelet has one or more florets (dry, single seeded flowers) surrounded by 2 bracts (a lower lemma and a small, upper palea)
  • Lemmas and/or glumes may have needle-like, stiff hairs (awns)
  • Florets have 3 stamens (pollen organs) and 2 feathery stigmas (tip of a female organ for receiving pollen) but lack showy petals and sepals as they are wind pollinated
  • Fruit is a seed-like grain enclosed in the bracts (called chaff in cereal grains)
  • Well-known members of this family include cereal grains such as wheat (Triticum spp.), corn (Zea spp.), rice (Oryza spp.), and oats (Avena spp.)
Growth habitat: 

Short-lived, perennial bunchgrass, 20–80 cm tall (occasionally up to 130 cm), that forms dense tufts from fibrous roots.  Also called hair bentgrass.

Leaves and stems: 

Leaves and stems are rough (scabrous) to touch.  Flowering stems are slender and erect with nodes that are purplish in color.  Short, narrow leaves, 1–3 mm wide and 4–14 cm long, are mainly basal and flat (or sometimes folded).  The thin, papery ligule, 2–5 mm long, at the base of the leaf sheath is well developed, ragged-edged or rough at the top, and usually rounded at the tip.  Lacks auricles, or small, clasping appendages on the collar of the leaf sheath.

Flowers: 

Flower cluster is a large, 10–30 cm long and nearly as wide (highly variable in size), purple or light brown, delicate and diffuse, upright panicle with brittle, hair-like, widely spreading branches.  Branches are rough to the touch, often crimped in a zigzag pattern, and frequently detach at maturity.  Spikelets grow near branch tips.  Spikelets are enclosed within a pair of equal-sized glumes, 1.5–3 mm long, and have 1 nerve, short hairs on the keels, and lack awns.  A single floret is present in each spikelet with one lemma, 1.5–2 mm long, that is awnless (or occasionally has a fine awn) and 5–7 nerves.  Florets lack a palea (upper lemma) or have a palea that is less than 1/4 as long as the lemmas.  Pollen sacs (anthers) are 0.4–0.7 mm long.  The flower cluster often breaks away with age and rolls along the ground like a tumbleweed in the wind.  In dense patches, the purplish hue of flower clusters can often be seen from a distance.  Touching the panicle to your skin will reveal why one of its common names is ticklegrass.

Roots: 

Fibrous roots are not rhizomatous.  Reproduces by seed and vegetatively by stolons.

Seeds: 

A single, tiny, dry seed in each floret is light brown and longitudinally grooved.

Habitat preferences: 

Moist to dry, open and often disturbed sites such as forest openings, clearings, roadsides, grasslands, meadows, wetlands, dry, rocky slopes and gravelly river bars in low to alpine elevations.    

Interesting facts: 

The name scabra means “rough” or “scabrous” and refers to the roughness of the foliage.  Elk (Cervus elaphus), moose (Alces alces), deer (Cervidae spp.), pronghorn (Antilocapra americana), small mammals, upland game birds, and waterfowl (Anseriformes) occasionally graze rough bentgrass.  Prior to flowering, livestock readily use it for forage.  Rough bentgrass occurs in both thermal and non-thermal habitats in Yellowstone National Park, but has a shorter growing season in thermal habitats than in non-thermal habitats.

Rough bentgrass is a pioneer plant in burned areas; its wind-dispersed seeds readily colonize recently burned sites from adjacent areas and occasionally, seeds that survived the fire in the soil germinate and establish.  Disturbed sites can be re-seeded with rough bentgrass as its ability to grow in a wide range of habitat types from wetland meadows to alpine turf is a great advantage.  Its fibrous root system makes it effective in preventing soil erosion.  Rough bentgrass often thrives on industrially damaged sites, such as abandoned coal-mine sites, and areas with high sulfur emissions.

Biological Classification: