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Yavapai County Native & Naturalized Plants

Agrostis gigantea - redtop

Synonyms: Agrostis alba

Other Common Names: redtop bentgrass, black bent, water bentgrass

Plant Form:Grass

Family: Poaceae

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Seedheads and blades

Max Licher @, Usage Rights: Creative Commons Attribution-ShareAlike (CC BY-SA)
Plant image

Max Licher @, Usage Rights: Creative Commons Attribution-ShareAlike (CC BY-SA)
  Grass Description -   Glossary of Grass Terminology

Origin: Introduced    Season: Cool
Habitat Description: Areas with shallow water, wet meadows, grasslands, and along stream banks.
Plant Communities: Semidesert Grasslands, Riparian
Elevation: 3850 - 7290 feet

General Description

Desc: Redtop can be distinguished from other bent grasses by its colorful purplish-red seedhead. Other bent grasses have a seedhead that is green or gray and their leaf blades are narrower.
Identification notes: Rhizomes; seedhead stem 8 to 47 inches tall; seedhead 3 to 11 inches long, less than 1/2 the length of the seedhead stem, open at flowering otherwise contracted. One-flowered spikelets. Ligules of the upper leaves less than 1/4 inch long.
Grass Type: Perennial mat or sod-forming  Rhizomes: Y  Stolons: N
Large Dense Clump (> 2 feet): N  Bushy (highly branched): N
Height with Seedheads: Greater than 36 inches
Seedhead Structure: Branched - fingerlike  Seedhead Droops: N
Flowering Period: Mar - Apr

Flower Characteristics

Number of Flowers per Spikelet: One-flowered  Spikelets One-sided: N
Awns: Absent   Three Awns: N  Awns Bent: N

Flower and Seedhead Notes: Loose panicles, taller than wide, 3 to 11 inches long, egg-shaped to pyramidal. Spikelets are typically purplish red, somewhat flattened, lance-shaped tapering to a pointed tip, with a single floret and a short, straight, rough-textured stalk.

Vegetative Characteristics

Blade Hairy: N  Blade with White Margin: N  Blade Cross Section: Flat or folded  
Blade Notes: Leaves are alternate, 2 to 8 inches long, up to 1/3 inch wide, flat, hairless and mostly smooth on both surfaces.
Sheath Hairy: N  Tuft of Hairs Top of Sheath or Collar: N  Ligules: Membranous
Auricles (Ear-like lobes at base of blades): N
Vegetative Notes: Sheaths are mostly smooth; edges overlapping near the tip forming a long ā€œVā€ at the front. The ligule is longer than wide, the top edge rounded to straight across and slightly jagged.

Forage Value: Cattle prefer nearly all other cultivated grasses to redtop. It is commonly used for erosion control in plantings along riparian zones and wetlands.

  Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr #C
Prescott, AZ 86305
(928) 445-6590
Version 8.0  
Last Updated: Nov 21, 2021
Content Questions/Comments: Email Mary Barnes  
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