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Patrick Alexander @
Yavapai County Native & Naturalized Plants

Achnatherum robustum - sleepygrass

Synonyms: Stipa robust

Plant Form:Grass

Family: Poaceae

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Plant - summer

Patrick Alexander @
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Patrick Alexander @
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Patrick Alexander @
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Hairy collar and ligule

Patrick Alexander @
  Grass Description -   Glossary of Grass Terminology

Origin: Native    Season: Warm
Habitat Description: Dry plains and hills, open woods and forest clearings, and along roadsides.
Plant Communities: Desert Scrub, Interior Chaparral, Semidesert Grasslands, Pinyon Juniper Woodland, Montane Conifer Forest, Disturbed Areas
Elevation: 4000 - 8000 feet

Similar Species: A. nelsonii

General Description

Desc: Stems erect or ascending (curving upward) and growing in dense tufts or clusters, without rhizomes. Leaves mostly below the middle of the stem in 2 vertical ranks on opposite sides of the stem.
Identification notes: Sheath collars are very hairy. The lower nodes of the seedhead are also hairy. Plant is robust, often more than 3 feet tall. Glumes are firm.
Grass Type: Perennial bunchgrass  Rhizomes: N  Stolons: N
Large Dense Clump (> 2 feet): N  Bushy (highly branched): N
Height with Seedheads: Greater than 36 inches
Seedhead Structure: Branched - contracted  Seedhead Droops: N
Flowering Period: Jun - Sep

Flower Characteristics

Number of Flowers per Spikelet: One-flowered  Spikelets One-sided: N
Awns: Greater than 1 inch   Three Awns: N  Awns Bent: Y

Flower and Seedhead Notes: Inflorescence a tight, contracted panicle, with 1 spike or cluster per stem. Awns 3/4 to 1-1/2 inches long or longer, twisted like a corkscrew, and twice geniculate (bent twice).

Vegetative Characteristics

Blade Hairy: N  Blade with White Margin: N  Blade Cross Section: Flat or involute  
Blade Notes: Linear leaf blades 1/8 to 3/8 inch wide and hairless. Leaf blades mostly flat with the margins rolled inward. Bottom surface smooth, top surface roughly ribbed.
Sheath Hairy: N  Tuft of Hairs Top of Sheath or Collar: Y  Ligules: Membranous
Auricles (Ear-like lobes at base of blades): N
Vegetative Notes: Basal sheaths mostly smooth, margin tips minutely hairy. Collars hairy, those of the flag leaves densely hairy, sides glabrous. Ligules smooth and truncated, rounded, or obtuse; upper ligules twice as long as basal ligules.

Forage Value: Contains diacetone alcohol which can be poisonous to livestock, hence the common name sleepygrass.

  Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr #C
Prescott, AZ 86305
(928) 445-6590
Version 8.0  
Last Updated: Feb 16, 2020  
Content Questions/Comments: Email Jeff Schalau  
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