Agrostis

Agrostis Agrostis 2 Agrostis 3 Agrosits 4

(Pictured from left to right: Agrostis gigantea (2 photos), Agrostis hyemalis, and Agrostis stolonifera)

This genus is characterized by small spikelets with a single floret. Inflorescences are open panicles. Glumes are acute or acuminate with the first usually 1-nerved and the second 1- or 3-nerved; awnless; often as long as, or longer than, the floret. Lemmas may be awnless or awned from below the middle. Paleas usually are absent or very small; rarely well-developed.

There are 4 species in MN; 2 native. 

Common species:
Agrostis gigantea (ah gros' tis ji gan tea' ah)

  • Synonyms: A. stolonifera var. major; A. alba
  • Common names: red-top, summer dew grass, white-top
  • Origin and habitat: Introduced from Europe; open moist places, especially along roadsides
  • Identifying characters: This is a stiff-looking, colonial perennial (rhizomatous and occasionally forming stolons) with reddish or purplish spreading inflorescences. Inflorescences can be up to 8 cm long. Leaf sheaths have a transparent margin near the collar area and the ligules are fairly long (1.5-4 mm). Spikelets are 2-3.5 mm long.
  • Comments: Red-top's reddish color and colonial habit are its most distinctive character and ones that sets this species apart from nearly all others. The species was introduced into this country for hay and has widely escaped, often becoming a dominant species in old fields. Redtop can tolerate some inundation, particularly in the spring. The name A. alba (found in "Gray's Manual") was an illegitimate one (Voss, E.G., 1966, Nomenclatural notes on monocots, Rhodora 68: 435-463) and according to the "International Code of Botanical Nomenclature" had to be changed. 

Agrostis hyemalis (ah gros' tis hi eh mah' lis)

  • Synonyms: A. hiemalis, A. scabra, A. geminata
  • Common names: fire grass, hair grass, rough-leaved bent, silk grass, tickle grass
  • Origin and habitat: Native; variety of open habitats especially where the soil dries periodicallyIdentifying characters: Often forming large colonies, this species is quite wispy or wiry in appearance. The clustered stems are minutely pubescent just below the nodes and the ligules are quite long (up to 3 mm). The inflorescence is often as much as half the length of the whole plant and frequently pinkish in color. Spikelets are smaller than in the previous species, 1.2-3.2 mm long.
  • Comments: A form with somewhat shorter inflorescence branches and a more tufted habit has been separated as A. geminata (on the state rare list). It is now considered to be a minor variant within this wide-ranging species (Dore, W.G. and J. McNeill, 1980, Grasses of Ontario, Monograph 26, Research Branch Agriculture Canada; Holmgren, 1977, Intermountain Flora, Vol. 6, Columbia Univ. Press, NY, p.280). Hair grass is a much finer, more delicate species than red-top and its color is definitely more subdued. This is a species of open sites and has often been found after recent fires, hence the common name of fire grass

Maps

Agrostis giganteaAgrostis hyemalisAgrostis stolonifera

Additional Species in Minnesota:
A. perennans
A. stolonifera

Copyright 2002, A.F. Cholewa, J.F. Bell Museum of Natural History, University of Minnesota / No portion of this guide may be duplicated without written permission of author.