Monocotyledon species found in Montana number at least 615. The Montana Natural Heritage Program has identified a number of monocot species as Species of Concern.Species of Concern are native taxa that are at-risk due to declining population trends, threats to their habitats, restricted distribution, and/or other factors. Designation as a Montana Species of Concern or Potential Species of Concern is based on the Montana Status Rank, and is not a statutory or regulatory classification. Rather, these designations provide information that helps resource managers make proactive decisions regarding species conservation and data collection priorities. See the latest Species of Concern Reports for more detailed explanations and assessment criteria.

Monocotyledons are one of two major groups of flowering plants (or angiosperms) that are traditionally recognized, the other being dicotyledons, or dicots. Monocot seedlings typically have one cotyledon (seed-leaf), in contrast to the two cotyledons typical of dicots. Monocots have been recognized at various taxonomic ranks, and under various names (see below). The APG II system recognises a clade called "monocots" but does not assign it to a taxonomic rank. There are between 50,000 and 60,000 species within this group; according to IUCN there are 59,300 species. The largest family in this group (and in the flowering plants as a whole) by number of species are the orchids (family Orchidaceae), with more than 20,000 species.Peter H. Raven; Ray Franklin Evert; & Susan E. Eichhorn. (2005) Biology of Plants, 7th ed., page 459 In agriculture the majority of the biomass produced comes from monocots. The true grasses, family Poaceae (Gramineae), are the most economically important family in this group. These include all the true grains (rice, wheat, maize, etc.), the pasture grasses, sugar cane, and the bamboos. True grasses have evolved to become highly specialised for wind pollination. Grasses produce much smaller flowers, which are gathered in highly visible plumes (inflorescences). Other economically important monocot families are the palm family (Arecaceae), banana family (Musaceae), ginger family (Zingiberaceae) and the onion family Alliaceae, which includes such ubiquitously used vegetables as onions and garlic.

Arrow-grass family Order: Najadales, family: Juncaginaceae Common bog arrow-grass, Triglochin maritima Flowering quillwort, Triglochin scilloides Slender bog arrow-grass, Triglochin palustris

Arum family Order: Arales, family: Araceae Yellow skunk-cabbage, Lysichiton americanus

Bur-reeds Order: Typhales, family: Sparganiaceae Branching bur-reed, Sparganium androcladum Large bur-reed, Sparganium eurycarpum Narrowleaf bur-reed, Sparganium angustifolium Small bur-reed, Sparganium natans

Cattails Order: Typhales, family: Typhaceae Broadleaf cattail, Typha latifolia Narrow-leaved cattail, Typha angustifolia

Ditch-grass family Order: Najadales, family: Ruppiaceae Ditch-grass, Ruppia maritima

Duckweeds Order: Arales, family: Lemnaceae Columbia water-meal, Wolffia columbiana Dotted watermeal, Wolffia borealis Duck-meal, Spirodela polyrrhiza Lesser duckweed, Lemna minor Pale duckweed, Lemna valdiviana Spotted water-meal, Wolffia brasiliensis Star duckweed, Lemna trisulca Turion duckweed, Lemna turionifera

Flowering-rush family Order: Alismatales, family: Butomaceae Flowering-rush, Butomus umbellatus

Grasses Order: Cyperales, family: Poaceae Alaskan oniongrass, Melica subulata Alkali cordgrass, Spartina gracilis Alkali muhly, Muhlenbergia asperifolia Alkali sacaton, Sporobolus airoides Alpine bluegrass, Poa alpina American mannagrass, Glyceria grandis American sloughgrass, Beckmannia syzigachne Annual bluegrass, Poa annua Annual false wheatgrass, Eremopyrum triticeum Annual hairgrass, Deschampsia danthonioides Annual muhly, Muhlenbergia minutissima Arctic bluegrass, Poa arctica Awnless wild rye, Elymus submuticus Baffin fescue, Festuca baffinensis Banff loose-flowered bluegrass, Poa laxa ssp. banffiana Barnyard grass, Echinochloa crus-galli Basin brome, Bromus polyanthus Beardless oats, Trisetum wolfii Beardless wild rye, Leymus triticoides Bermudagrass, Cynodon dactylon Big bluestem, Andropogon gerardii Blue grama, Bouteloua gracilis Blue wild rye, Elymus glaucus Blue-joint reedgrass, Calamagrostis canadensis Bluebunch wheatgrass, Pseudoroegneria spicata Bog bluegrass, Poa leptocoma Boreal mannagrass, Glyceria borealis Bottlebrush squirrel-tail, Elymus elymoides Bristly bristle grass, Setaria verticillata Bristly dogtail grass, Cynosurus echinatus Broad-glumed brome, Bromus latiglumis Brome fescue, Vulpia bromoides Brook grass, Catabrosa aquatica Buffalo grass, Bouteloua dactyloides Bulbous bluegrass, Poa bulbosa California brome, Bromus carinatus California oatgrass, Danthonia californica Canada bluegrass, Poa compressa Canada wild rye, Elymus canadensis Cascade reedgrass, Calamagrostis tweedyi Cheatgrass, Bromus tectorum Chilean brome, Bromus berteroanus Colonial bentgrass, Agrostis capillaris Columbia needlegrass, Stipa nelsonii ssp. dorei Common barley, Hordeum vulgare Common canary grass, Phalaris canariensis Common hardgrass, Sclerochloa dura Common reed, Phragmites australis Common velvetgrass, Holcus lanatus Contracted Indian ricegrass, Oryzopsis contracta Corn brome, Bromus squarrosus Creeping foxtail, Alopecurus arundinaceus Crested dogtail grass, Cynosurus cristatus Crested wheatgrass, Agropyron cristatum Cultivated oat, Avena sativa Cultivated rye, Secale cereale Cultivated wheat, Triticum aestivum Cusick's bluegrass, Poa cusickii Darnel ryegrass, Lolium temulentum Dense pine reedgrass, Calamagrostis koelerioides Dense silky bentgrass, Apera interrupta Ditch reedgrass, Calamagrostis scopulorum Drooping woodreed, Cinna latifolia Eastern wild rice, Zizania aquatica False buffalograss, Monroa squarrosa Few-flowered oatgrass, Danthonia unispicata Few-flowered panic-grass, Dichanthelium oligosanthes Field brome, Bromus arvensis Fowl bluegrass, Poa palustris Fowl mannagrass, Glyceria striata Fox-tail timothy, Crypsis alopecuroides Foxtail barley, Hordeum jubatum Foxtail fescue, Vulpia myuros Foxtail muhly, Muhlenbergia andina Fringed brome, Bromus ciliatus Great Basin wild rye, Leymus cinereus Green bristle grass, Setaria viridis Green needlegrass, Stipa viridula Hairy crabgrass, Digitaria sanguinalis Ice grass, Phippsia algida Idaho bentgrass, Agrostis idahoensis Idaho fescue, Festuca idahoensis Indian goosegrass, Eleusine indica Indian ricegrass, Oryzopsis hymenoides Indiangrass, Sorghastrum nutans Inland bluegrass, Poa interior Intermediate wheatgrass, Thinopyrum intermedium Italian foxtail, Setaria italica Italian ryegrass, Lolium multiflorum Japanese brome, Bromus japonicus Johnson grass, Sorghum halepense Jointed goatgrass, Aegilops cylindrica Kentucky bluegrass, Poa pratensis Leafy bentgrass, Agrostis pallens Lemmon's alkaligrass, Puccinellia lemmonii Lemmon's needlegrass, Stipa lemmonii Letterman's bluegrass, Poa lettermanii Letterman's needlegrass, Stipa lettermanii Little barley, Hordeum pusillum Little bluestem, Schizachyrium scoparium Little lovegrass, Eragrostis minor Little ricegrass, Oryzopsis exigua Littleseed ricegrass, Oryzopsis micrantha Long-spine sandbur, Cenchrus longispinus Marsh muhly, Muhlenbergia racemosa Mat muhly, Muhlenbergia richardsonis Meadow barley, Hordeum brachyantherum Meadow fescue, Festuca pratensis Meadow foxtail, Alopecurus geniculatus Meadow foxtail, Alopecurus pratensis Meadow timothy, Phleum pratense Mediterranean or sea barley, Hordeum marinum Missoula County oats, Trisetum x orthochaetum Montana wheatgrass, Elymus albicans Mountain bentgrass, Agrostis humilis Mountain fescue, Festuca viridula Mountain foxtail, Alopecurus alpinus Mountain hairgrass, Vahlodea atropurpurea Mountain muhly, Muhlenbergia montana Mountain timothy, Phleum alpinum Mouse barley, Hordeum murinum Mt. Washington bluegrass, Poa laxa Muttongrass, Poa fendleriana Narrow false oats, Trisetum spicatum Narrow-flower bluegrass, Poa stenantha Narrow-flowered brome, Bromus vulgaris Needle-and-thread, Stipa comata Nelson's needlegrass, Stipa nelsonii Nevada needlegrass, Stipa nevadensis Nodding bluegrass, Poa reflexa Nodding fescue, Festuca subulata Nodding trisetum, Trisetum canescens Northern bentgrass, Agrostis borealis Northern fescue, Festuca viviparoidea Northern sweet grass, Hierochloe hirta Northern wild rye, Leymus innovatus Nuttall's alkali grass, Puccinellia nuttalliana Oniongrass, Melica bulbosa Orchard grass, Dactylis glomerata Oregon bentgrass, Agrostis oregonensis Pale manna grass, Puccinellia pauciflora Panic grass, Dichanthelium acuminatum Parry's oatgrass, Danthonia parryi Patterson's bluegrass, Poa abbreviata ssp. pattersonii Perennial ryegrass, Lolium perenne Persian ryegrass, Lolium persicum Pineforest needlegrass, Stipa pinetorum Pinegrass, Calamagrostis rubescens Plains muhly, Muhlenbergia cuspidata Plains reedgrass, Calamagrostis montanensis Plains rough fescue, Festuca hallii Porcupine needlegrass, Stipa spartea Porter's brome, Bromus porteri Poverty oatgrass, Danthonia spicata Prairie bluegrass, Poa arida Prairie cordgrass, Spartina pectinata Prairie dropseed, Sporobolus heterolepis Prairie junegrass, Koeleria macrantha Prairie sandreed, Calamovilfa longifolia Prairie wedgegrass, Sphenopholis obtusata Proso millet, Panicum miliaceum Pullup muhly, Muhlenbergia filiformis Pumpelly's brome, Bromus inermis ssp. pumpellianus Purple lovegrass, Eragrostis pectinacea Purple oat, Schizachne purpurascens Purple reedgrass, Calamagrostis purpurascens Purple three-awn grass, Aristida purpurea Quackgrass, Elymus repens Rabbit's-foot grass, Polypogon monspeliensis Rattlesnake brome, Bromus briziformis Red fescue, Festuca rubra Redtop, Agrostis stolonifera Reed canary grass, Phalaris arundinacea Rice cutgrass, Leersia oryzoides Richardson's needlegrass, Stipa richardsonii Rocky Mountain fescue, Festuca saximontana Rough barnyard grass, Echinochloa muricata Rough bentgrass, Agrostis scabra Rough bluegrass, Poa trivialis Rough fescue, Festuca scabrella Roughleaf ricegrass, Oryzopsis asperifolia Russian wild rye, Psathyrostachys juncea Rye brome, Bromus secalinus Saltgrass, Distichlis spicata Sand bluestem, Andropogon hallii Sand dropseed, Sporobolus cryptandrus Sand wild rye, Leymus flavescens Sandberg bluegrass, Poa secunda Scribner's panic grass, Dichanthelium oligosanthes var. scribnerianum Scribner's wild rye, Elymus scribneri Sheathed dropseed, Sporobolus vaginiflorus Sheep fescue, Festuca ovina Short-awn foxtail, Alopecurus aequalis Short-leaved bluegrass, Poa arnowiae Shortleaf fescue, Festuca brachyphylla Showy oniongrass, Melica spectabilis Side-oats grama, Bouteloua curtipendula Six-weeks grama, Bouteloua barbata Six-weeks fescue, Vulpia octoflora Slender hairgrass, Deschampsia elongata Slender oat, Avena barbata Slender wedgegrass, Sphenopholis intermedia Slender wheatgrass, Elymus trachycaulus Slimstem reedgrass, Calamagrostis stricta Small dropseed, Sporobolus neglectus Small six-weeks fescue, Vulpia microstachys Smallflower fescue, Festuca minutiflora Smith's melicgrass, Melica smithii Smooth brome, Bromus inermis ssp. inermis Smooth crabgrass, Digitaria ischaemum Soft brome, Bromus hordeaceus Spike bentgrass, Agrostis exarata Spike fescue, Leucopoa kingii Spike muhly, Muhlenbergia glomerata Spike-oat, Helictotrichon hookeri Spiked brome, Bromus racemosus Sprangletop, Leptochloa fusca Sprangletop, Scolochloa festucacea Spreading alkali grass, Puccinellia distans Stinkgrass, Eragrostis cilianensis Stout wood reed-grass, Cinna arundinacea Sweet vernalgrass, Anthoxanthum odoratum Switchgrass, Panicum virgatum Tall dropseed, Sporobolus compositus