USGS - science for a changing world

Northern Prairie Wildlife Research Center

  Home About NPWRC Our Science Staff Employment Contacts Common Questions About the Site

Aquatic and Wetland Vascular Plants of the Northern Great Plains

Poaceae - The Grass Family

Perennial or annual, rhizomatous or tufted plants with long, linear, parallel-veined leaves arranged alternately in 2 vertical ranks on a terete (rarely compressed), usually hollow stem with swollen, solid nodes; leaf sheaths commonly open longitudinally, the margins overlapping (sheaths tubular with the margins united in Bromus and Glyceria); a membranous or hairy ligule projecting between the blade and the culm from the summit of the sheath, this sometimes absent. Flowers much reduced, perfect or rarely unisexual (the plants then monoecious or dioecious), each subtended by 2 bracts, the larger one (lemma) containing the flower, the smaller one (palea) covering the flower, palea rarely absent, the lemma and palea often adhering to and enclosing the ripe grain, the flower and its surrounding lemma and palea collectively termed the floret; perianth rudimentary, represented by no more than 2 (in taxa of this region) inner, obscure scales (lodicules), these usually undetectable; stamens usually 3(1-6); ovary superior, 1-celled, never enclosed in a sac; styles bifid, the stigmas plumose; ovule 1, usually parietal. Florets arranged in spikelets, these consisting of 1-many florets which are sessile on a shortened axis (rachilla), the lowest 2 bracts of the spikelet empty (the glumes), these rarely absent, often unequal, the lowermost of the glumes usually smaller and called the first glume, the upper one called the second glume, the glumes seldom equal and opposite. Spikelets arranged in a variety of inflorescence types, the most common being a panicle in which the spikelets are individually pedicelled in a branching inflorescence, or less often, the spikelets sessile on a rachis in one or more spikes; if solitary, the spike terminal, or if more than one, the spikes 1-sided (the spikelets all attached to one side of the rachis) and arranged in a raceme or panicle; spikelets disarticulating either above or below the glumes at maturity, the glumes remaining attached in the inflorescence if disarticulation occurs above the glumes, or the glumes falling with the florets (and sometimes with other parts of the inflorescence attached) if disarticulation is below the glumes.

Poaceae is the second largest family in our region, with most species characteristic of prairie, but many also occurring in wetland and woodland habitats. The family is rife with species that occur in a broad array of moisture regimes and many of those are included here.


Hitchcock, A. S.  1971.  Manual of the grasses of the United States.  Vol. 1 
     and 2.  Revised by Agnes Chase.  Dover Publications, Inc., New York. 

Pohl, R. W.  1978.  How to know the grasses, third edition.  Wm. C. Brown 
     Publishers, Dubuque, Iowa.
Lead Characteristic Go To
1 Spikelets containing 2 or more functional florets (many may contain only 1 floret in Catabrosa). Lead 2
1 Spikelets containing 1 functional floret. Lead 16
2 Tall, stout reeds over 2 m tall, with a large plumelike panicle; rachillas hairy. Genus Phragmites
2 Plants without the above combination of characters. Lead 3
3 Inflorescence a simple, terminal spike, the spikelets sessile on an unbranched rachis. Genus Agropyron
3 Inflorescence of variously branched types, usually a panicle, if appearing spikelike, then the spikelets individually pedicelled. Lead 4
4 Glumes both as long as or exceeding the lowest floret, often as long as the entire spikelet; lemmas awned from the back or awnless. Lead 5
4 Glumes, or at least the first one, shorter than the first floret; lemmas awned from the tip or awnless. Lead 8
5 Lemmas awned from below the middle of the back. Genus Deschampsia
5 Lemmas awnless. Lead 6
6 Florets bearded on the callus; spikelets disarticulating above the glumes. Genus Scolochloa
6 Florets glabrous on the callus; spikelets disarticulating below the glumes. Lead 7
7 Glumes alike, both inflated and broadly boat-shaped; spikelets nearly round in outline. Genus Beckmannia
7 Glumes dissimilar, the second much broader than the first; spikelets not round. Genus Sphenopholis
8 Spikelets all sessile or very short-pedicelled in an inflorescence of several to many straight branches, much of the inflorescence often enclosed by leaf sheaths. Genus Leptochloa
8 Spikelets, or at least some of them, obviously pedicelled, borne in an open to contracted panicle. Lead 9
9 Spikelets unisexual (plants dioecious), in a simple, contracted panicle; low rhizomatous perennial of saline or alkaline soils. Genus Distichlis
9 Spikelets bisexual, in an open to contracted panicle; plants of various habits and habitats. Lead 10
10 Lemmas prominently 3-nerved. Lead 11
10 Lemmas faintly to prominently 5- to 7-nerved. Lead 12
11 Spikelets 2-flowered (many may be 1-flowered); lemmas truncate and erose at the tip. Genus Catabrosa
11 Spikelets several- to many-flowered; lemmas acute-tipped. Genus Eragrostis
12 Callus of the florets bearded with short, stiff hairs. Genus Scolochloa
12 Callus not bearded, although cobwebby hairs may be present at the base of the lemma. Lead 13
13 Lemmas awned. Genus Bromus
13 Lemmas awnless. Lead 14
14 Lemmas prominently 7-nerved. Genus Glyceria
14 Lemmas faintly 5-nerved. Lead 15
15 Lemmas tapered to an acute to blunt tip, often with cobwebby hairs at the base and/or short-pubescent on the back; leaf blades with the margins and midrib converging to a blunt, keeled tip resembling the prow of a boat. Genus Poa
15 Lemmas little tapered to a blunt, often erose tip, glabrous; leaf blades flat or involute and pointed at the tip. Genus Puccinellia
16 Glumes absent. Lead 17
16 Glumes present. Lead 18
17 Spikelets unisexual, terete, the pistillate above the staminate in a large panicle; leaves smooth. Genus Zizania
17 Spikelets bisexual, strongly compressed; leaves strongly scabrous, abrasive to the touch. Genus Leersia
18 Spikelets containing 1 fertile floret and 1 or 2 sterile or staminate florets below the fertile one (the 2 lower florets represented by a pair of tiny, villous scales appressed to the base of the fertile lemma in Phalaris, otherwise the lower floret or florets more lemmalike or glumelike). Lead 19
18 Spikelets containing a single fertile floret only (some reduced sterile spikelets may be present). Lead 22
19 Spikelets disarticulating above the glumes, the 2 lower florets falling with the fertile one as a unit. Lead 20
19 Spikelets disarticulating below the glumes, the entire spikelet falling with the fertile floret and the single, glumelike sterile floret intact. Lead 21
20 Lower florets sterile, reduced to a pair of villous scales at the base of the hard, shiny fertile one. Genus Phalaris
20 Lower florets staminate, longer than the fertile one and enclosing it, similar to the fertile floret in texture Genus Hierochloe
21 Spikelets crowded in few to many densely flowered branches; glumes and lemmas with stout, stiff hairs. Genus Echinochloa
21 Spikelets widely spreading in an open panicle; glumes and lemmas glabrous or merely scabrous on the nerves. Genus Panicum
22 Spikelets sessile or essentially so on one or more rachises, the infloresence a terminal spike or of several to many 1-sided spikes arranged in a raceme or panicle. Lead 23
22 Spikelets borne on pedicels in an open or contracted panicle, the panicle sometimes dense and spikelike. Lead 25
23 Inflorescence a terminal spike; lemmas with awns several times longer than the body; glumes awn-like. Genus Hordeum
23 Inflorescence of several to many 1-sided spikes arranged in a raceme or panicle; glumes awnless or with awns shorter than the body. Lead 24
24 Glumes unequal, narrow; spikes in a terminal raceme. Genus Spartina
24 Glumes equal, broadly boat-shaped; spikes in a narrow panicle. Genus Beckmannia
25 Spikelets disarticulating below the glumes, falling as an entire unit. Lead 26
25 Spikelets disarticulating above the glumes, the glumes remaining after the florets have fallen. Lead 29
26 Glumes awned. Lead 27
26 Glumes awnless. Lead 28
27 Awns of the glumes several times longer than the body. Genus Polypogon
27 Awns of the glumes shorter than the body. Genus Phleum
28 Panicle dense, cylindric and spikelike. Genus Alopecurus
28 Panicle more open, not cylindric or spikelike. Genus Cinna
29 Lemmas awned from the back, bearded on the callus, 5-nerved. Genus Calamagrostis
29 Lemmas awnless or awned from the tip, glabrous or pilose toward the base, 3-nerved. Lead 30
30 Floret equal to or exceeding one or both glumes (excluding awns, if present); lemmas strongly nerved. Genus Muhlenbergia
30 Floret exceeded by both glumes; lemmas very faintly nerved. Genus Agrostis

63. Poaceae, the Grass Family
1. Agropyron Gaertn. -- Wheatgrass
1. Agropyron repens (L.) Beauv. -- Quackgrass
2. Agrostis L. -- Bentgrass
1. Agrostis exarata Trin. -- Spikebent
2. Agrostis hyemalis (Walt.) B.S.P. -- Ticklegrass
3. Agrostis stolonifera L. -- Redtop
3. Alopecurus L. -- Foxtail
1. Alopecurus aequalis Sobol. -- Short-awn foxtail
2. Alopecurus arundinaceus Poir. -- Creeping foxtail
3. Alopecurus carolinianus Walt. -- Carolina foxtail
4. Alopecurus geniculatus L. -- Water foxtail
5. Alopecurus pratensis L. -- Meadow foxtail
4. Beckmannia Host
1. Beckmannia syzigachne (Steud.) Fern. -- Western sloughgrass
5. Bromus L. -- Brome grass
1. Bromus ciliatus L. -- Fringed brome
6. Calamagrostis Adans. -- Reedgrass
1. Calamagrostis canadensis (Michx.) Beauv. -- Bluejoint reedgrass
2. Calamagrostis stricta (Timm) Koel. -- Northern reedgrass
7. Catabrosa Beauv.
1. Catabrosa aquatica (L.) Beauv. -- Brookgrass
8. Cinna L. -- Woodreed
1. Cinna arundinacea L. -- Woodreed
2. Cinna latifolia (Trev. ex Goepp.) Griseb. -- Drooping woodreed
9. Deschampsia Beauv. -- Hairgrass
1. Deschampsia cespitosa (L.) Beauv. -- Tufted hairgrass
10. Distichlis Raf.
1. Distichlis spicata (L.) Greene -- Saltgrass
11. Echinochloa Beauv. -- Barnyardgrass
1. Echinochloa crusgalli (L.) Beauv.
2. Echinochloa muricata (Beauv.) Fern.
12. Eragrostis Beauv. -- Lovegrass
1. Eragrostis hypnoides (Lam.) B.S.P. -- Teal lovegrass
2. Eragrostis reptans (Michx.) Nees
13. Glyceria R. Br. -- Mannagrass
1. Glyceria borealis (Nash) Batch. -- Northern mannagrass
2. Glyceria grandis S. Wats. -- American mannagrass
3. Glyceria striata (Lam.) Hitchc. -- Fowl mannagrass
14. Hierochloe R. Br. -- Holygrass, sweetgrass
1. Hierochloe odorata (L.) Beauv.
15. Hordeum L. -- Barley
1. Hordeum jubatum L. -- Foxtail barley
16. Leersia Sw.
1. Leersia oryzoides (L.) Sw. -- Rice cutgrass
17. Leptochloa Beauv.
1. Leptochloa fascicularis (Lam.) A. Gray -- Bearded sprangletop
18. Muhlenbergia Schreb. -- Muhly
1. Muhlenbergia asperifolia (Nees & Meyen) Parodi -- Alkali muhly
2. Muhlenbergia glomerata (Willd.) Trin. -- Bristly muhly
3. Muhlenbergia mexicana (L.) Trin. -- Wirestem muhly
4. Muhlenbergia racemosa (Trin.) Rydb. -- Marsh muhly, green muhly
5. Muhlenbergia richardsonis (Trin.) Rydb. -- Mat muhly
19. Panicum L. -- Panic grass
1. Panicum capillare L. -- Common witchgrass
20. Phalaris L. -- Canarygrass
1. Phalaris arundinacea L. -- Reed canarygrass
21. Phleum L.
1. Phleum pratense L. -- Timothy
22. Phragmites Trin.
1. Phragmites australis (Cav.) Trin. ex. Steud. -- Common reed
23. Poa L. -- Bluegrass
1. Poa arida Vasey -- Plains bluegrass
2. Poa compressa L. -- Canada bluegrass
3. Poa palustris L. -- Fowl bluegrass
4. Poa pratensis L. -- Kentucky bluegrass
5. Poa trivialis L. -- Rough bluegrass
24. Polypogon Desf.
1. Polypogon monspeliensis (L.) Desf. -- Rabbitfoot beardgrass
25. Puccinellia Parl. -- Alkaligrass
1. Puccinellia cusickii Weatherby -- Cusick's alkaligrass
2. Puccinellia distans (L.) Parl. -- Weeping alkaligrass
3. Puccinellia nuttalliana (Schult.) Hitchc. -- Nuttall's alkaligrass
26. Scolochloa Link
1. Scolochloa festucacea (Willd.) Link -- Whitetop, sprangletop
27. Spartina Schreb. -- Cordgrass
1. Spartina gracilis Trin. -- Alkali cordgrass
2. Spartina pectinata Link -- Prairie cordgrass
28. Sphenopholis Scribn.
1. Sphenopholis obtusata (Michx.) Scribn. -- Prairie wedgegrass
29. Zizania L.
1. Zizania aquatica L. -- Annual wildrice

Previous Section -- Cyperaceae - The Sedge Family
Return to Contents
Next Section -- Sparganiaceae - The Burreed Family

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Webmaster
Page Last Modified: Saturday, 02-Feb-2013 06:37:23 EST
Sioux Falls, SD [sdww55]