Agrostis gigantea

Rhizomatous and sod-forming, to 10 or even 15 dm, not stoloniferous; larger (upper) ligules mostly 2.5-6 mm, higher than wide; lvs 3-8 mm wide; panicle 10-20 cm, notably suffused with purplish-red, at anthesis triangular-ovoid, with widely spreading, unequal branches, sometimes later more contracted; at least some of the panicle-branches floriferous to the base; panicle- branches and often even the pedicels scabrous; spikelets rather crowded, 2-3.5 mm; glumes scabrous along the keel; lemma two-thirds as long as the glumes, distally scabrous, awnless or seldom with a short dorsal awn; callus minutely bearded; palea half to two-thirds as long as the lemma; anthers 0.8-1.5 mm; 2n=42. Native of Europe, cult. and escaped into moist meadows, shores, coastal marshes, and other moist places throughout most of the U.S. and s. Can. (A. alba, misapplied; A. stolonifera var. major)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.

FNA 2007, USDA FEIS, Heil et al. 2013, Tilley et al 2010.

Common Name: redtop Duration: Perennial Nativity: Non-Native Lifeform: Graminoid General: Introduced perennial grass with rhizomes to 25 cm, erect stems 20-120 cm, sometimes geniculate at base, sometimes rooting at lower nodes, 4-7 nodes per culm. Vegetative: Leaves mostly cauline, sheaths smooth or sparsely minutely roughened, ligules longer than wide, dorsal surfaces usually scabrous, sometimes smooth, apices rounded to truncate, basal ligules 1-4.5 mm, upper ligules 2-7 mm; blades 4-10 cm long, 3-8 mm wide, Inflorescence: Panicles 8-25 cm long, less than half length of stem, 3-15 cm wide, erect open, ovate, lowest node with 3-8 branches; branches scabrous, spreading during and after anthesis, lower branches 4-9 cm, usually with many shorter secondary branches, resulting in crowding of spikelets; on pedicels 0.5-3.5 mm; spikelets narrowly ovate to lanceolate, green and slightly to strongly suffused with purple; glumes subequal, 1.5-3 mm, lanceolate, 1-veined, acute to apiculate, lower glumes scabrous on distal half of midvein, upper scabriculous on distal half of midvein; sparse callus hairs to 0.5 mm; lemmas 1.5-2.5 mm, 3-5 veined, veins obscure, usually unawned, but when awned, 0.5-1.5 mm straight awn. Ecology: Widespread and considered a serious weed, growing in fields, roads, ditches, other disturbed habitats. In the Southwest it grows above 5,000 ft (1524 m); flowers June to October. Distribution: Native to Europe and north Africa; naturalized throughout the US and Canada. Notes: Often confused with A. stolonifera, and sometimes treated as a variety of that species. A. gigantea has a panicle which remains open, while A. stolonifera-s panicle contracts after anthesis. Additionally, A. stolonifera has elongated leafy stolons which root at the nodes, and occasionally has short rhizomes. A. gigantea has no stolons but does have well-developed rhizomes. Can look like each other without inflorescences, so pay attention to the plant being rhizomatous or stoloniferous. A. gigantea is a preferred nesting habitat for prairie chickens, as their native prairie is now so scarce. The species was a commonly grown pasture grass throughout the US before 1940, and the NRCS continues to recommend its use for erosion control and as a pasture and turf grass. Ethnobotany: Unknown Etymology: Agrostis is from the Latin and Greek names for a type of grass, from Greek agron or agros, field or pasture, while gigantea means gigantic. Synonyms: Agrostis alba, Agrostis gigantea var. dispara, Agrostis nigra, Agrostis stolonifera subsp. gigantea, Agrostis stolonifera var. major Editor: SBuckley, 2010, AHazelton 2015