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Weedy and Invasive Grasses Found in Iowa

While Ralph Waldo Emerson may have viewed weeds as “plants whose virtues have not yet been discovered,” few farmers and gardeners take such a benevolent view of them. Weeds can be defined as plants growing where humans do not want them. A plant that grows very vigorously, crowding out other, perhaps more desirable, plants, may also be described as a weed. Iowa has a few native grasses that have weedy growth habits, but the majority of the weedy grasses in Iowa are exotics, grasses that have been introduced from other countries, or, as in the case of fall Panicum (Panicum dichotomiflorum), from another region of the United States. Exotic species are becoming a larger problem as more of them are becoming established in Iowa. An example is woolly cupgrass (Eriochloa villosa), introduced possibly 50 years ago and now becoming a major agricultural weed in Iowa. Particularly aggressive weeds may be labeled as noxious weeds—these are species that have been designated by legislation as being particularly damaging and needful of control measures. In this section, we present a list of the grasses in Iowa that most often fall into the weedy category, a “rogue’s gallery” or photo gallery of the 24 most common or most serious grass weeds in Iowa, and a list of frequently asked questions about grass weeds. We also provide links to other Web sites that contain more detailed information on weeds and weed control. Our aim is to assist in the identification of grass weeds in the state of Iowa.

Rogue's Gallery (24 most common weedy grasses)

Frequently Asked Questions

List of Weedy Grasses Found in Iowa


Federal government invasive species gateway website
APHIS Federal noxious weed program
Invaders Database University of Montana, Missoula
Invasive and Exotic Species of North America
Iowa State Weed Science
Iowa Noxious Weed Law
Plant Conservation Alliance Alien Plant Working Group
Weed Identification Illinois Council on Food and Agricultural Research
Weed Identification Guide Virginia Tech


Native Species

sandbur, longspine sandbur, mat sandbur (Cenchrus longispinus)

American barnyard grass (Echinochloa muricata)

foxtail barley (Hordeum jubatum)

wirestem muhly (Muhlenbergia frondosa)

nimblewill (Muhlenbergia schreberi)

witchgrass (Panicum capillare subsp. capillare)

knotroot foxtail (Setaria parviflora)

Non-native Species

smooth brome (Bromus inermis)

downy brome, cheatgrass (Bromus tectorum) listed as noxious in 35 states

smooth crabgrass (Digitaria ischaemum)

hairy crabgrass (Digitaria sanguinalis)

barnyard grass (Echinochloa crusgalli)

goosegrass (Eleusine indica)

quackgrass (Elymus repens) primary noxious weed in Iowa

stinkgrass (Eragrostis cilianensis)

woolly cupgrass (Eriochloa villosa) secondary noxious weed in MN

Amur silvergrass, plumegrass (Miscanthus sacchariflorus) escaped cultivation

fall panicum, kneegrass (Panicum dichotomiflorum) secondary noxious weed in MN

nodding foxtail, giant foxtail, Chinese foxtail (Setaria faberi) secondary noxious weed in Minnesota

foxtail millet, Hungarian millet (Setaria italica) escaped cultivation

yellow foxtail, yellow bristlegrass, pidgeongrass (Setaria pumila)

bur bristlegrass, bristly foxtail, hooked bristlegrass (Setaria verticillata)

green foxtail (Setaria viridis) designated as noxious in CO

shattercane, sudangrass (Sorghum bicolor) secondary noxious weed in Iowa, noxious in IN, MD, NV, OH, PA

Johnsongrass (Sorghum halepense) noxious in 18 states

Potentially Weedy Species in Iowa – Species to Watch

jointed goatgrass (Aegilops cylindrica) noxious in AZ, CA, CO, ID, NM, OR, WA

wild oats (Avena fatua) noxious in CO, secondary noxious in MN

southern crabgrass (Digitaria ciliaris)

nepalese browntop (Microstegium vimineum) not documented in Iowa, but has spread throughout the eastern half of the U.S.–description from the Alien Plant Working Group

fountaingrass (Pennisetum alopecuroides) escapes cultivation in some areas

crimson fountaingrass (Pennisetum setaceum) escapes cultivation in some areas

cogon grass (Imperata cylindrica) often called one of the world’s 10 worst weeds; red cultivar is relatively cold hardy and escapes cultivation in some areas –description from the Alien Plant Working Group

proso millet, broomcorn, hog millet (Panicum miliaceum) noxious in CO, secondary noxious weed in MN


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