Identification of the Primary Noxious Weeds of Minnesota - City of ...

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MINNESOTA NOXIOUS WEED LAWThe Minnesota Noxious Weed Law was enacted to protect the residents ofMinnesotafrom injurious effects of noxious weeds to public health, public roads, environment,crops, livestock, and other property. This law and related statutes areunder the general administration of the Commissioner of the Minnesota Departmentof Agriculture. Day-to-day or routine administration of the state's noxiousweed control program is carried out by the Director of the Agronomy ServicesDivision through the Supervisor of the Section of Weed Control. Implementationof the noxious weed law is accomplished through several Regulatory Investigatorslocated throughout the state. One of their primary duties is to see that localgovernments fulfill their responsibilities in the actual enforcement ofthe law. Theactual enforcement is carried out by local governments through local weed inspectorsin townships and cities and County Agricultural Inspectors in every Minnesotacounty.A noxious weed, as defined by Minnesota Law, is an annual, biennial, or perennialwhich is deemed by the Commissioner ofAgriculture to be injurious to publichealth, public roads, environment, crops, livestock, and other property. In Minnesota,there are ten weeds on the primary noxious weeds list. They are:Common NameBindweed, fieldHempIvy, poisonLoosestrife, purpleSpurge, leafySowthistle, perennialThistle, bullThistle, CanadaThistle, muskThistle, plumelessGenus and speciesConvolvulus arvensisCannabis sativaToxicodendron radicansLythrum salicaria, virgatum, orany combinationEuphorbia esulaSonchus arvensisCirsium vulgareCirsium arvenseCarduus nutansCarduus acanthoidesAccording to Minnesota law, these primary noxious weeds must be controlled onall private and public land in the state.2

INTRODUCTIONThis publicationwill be limited to the identification of the ten primary noxious weeds onthe primary noxiousweed list in Minnesota. This list includes six perennial, three biennial, and one annual weed.Annual weeds germinate and emerge from seed and complete their life cycle in one growing season. Annualweeds that complete their life cycle during the periodfrom springto fall are called summerannuals or justannuals.Annual weeds that complete their life cycle during the period from fall to spring are called winter annuals.There is only one annual weed on the Minnesota Noxious Weed list--hemp.Biennial weeds require two growing seasons to complete their life cycle. Biennials form a rosette (clusters ofleaves close to the ground) the first year and during the second year they develop a flower stalk, flower, produceseed, and then the plant dies. The three biennial weeds on the Minnesota Noxious Weed list are: bullthistle, musk thistle, and plumeless thistle.A perennial weed can live for 3 or more years. Perennial weeds may emerge from seed like annuals and biennials,but also emerge from rhizomes, stolons, or other underground storage organs. The six perennial weedsonthe Minnesota NoxiousWeedlist are: field bindweed,purpleloosestrife, poisonivy, leafy spurge, perennialsowthistle, Canada thistle.TABLE OF CONTENTSMinnesota Noxious Weed La''''' 2Introduction 3Glossary 14Additional References 14Secondary Noxious Weeds 15PRIMARY NOXIOUS WEEDSCommon NameGenus and SpeciesAnnual WeedsHempCannabis sativa 4Biennial WeedsBull ThistleMusk ThistlePlumelessThistleCirsium vulgare 5Carduus nutans 6Carduus acanthoides 7Perennial WeedsCanada ThistleField BindweedLeafy SpurgePerennial SowthistlePoison IvyPurple LoosestrifeCirsium arvensis 8Convolvulus arvensis 9Euphorbia esula 10Sonchus arvensis 11Toxicodendron radicans 12Lythrum salicaria, virgatum 133

BULL THISTLE[Cirsium vulgare (Savi) Tenore]COMPOSITE FAMILY - CompositaeDescription: Bull thistle growsmostoftenas a biennial,reproducingonlybyseed. Duringthefirstyear of growth, a large basal rosette with a largetap root is formed. During the second year ofgrowth, anerectflowering stem grows to a heightDf 2 to 4 feet. The stem is large, branched, and:overedwith dense hair. Leaf bases extend downthe stem to give the stem a winged appearance.The leaves are alternate, dark green, coarsely lobed,with 3 to 4 points per lobe, each ending in a longsharp spine. The upper surface of the leaf is:overed with short, stiff hairs and spines, and theunderside of the leaf is covered with dense, woolly,gray hair. The flower heads are compact, 1 to 2inches in diameter and each flower head is surroundedby spine-tipped bracts. The flowers arereddish-purple. Flowering occurs from late Junethrough August and the seed matures in Julythrough September. The seeds are 1/8 inch long,Dblong, flattened, and curved and are light brownwith dark brown stripes.Distribution: Bull thistle is primarily found inpastures, waste areas, and along roadsides. Bullthistle is found throughout Minnesota and canbefound on a variety of soil types.SeedlingLeafMature PlantSeed5

MUSK THISTLE(Carduus nutans L.)COMPOSITE FAMILY - CompositaeDescription: Musk thistle (also called noddingthistle) reproduces only by seed and grows mostoften as a biennial; however, it can occasionallygrow as a winter annual or annual. During thefirst year of growth, a large basal rosette with alarge tap rootisformed. Duringthe secondyearofgrowth, anerect flowering stem grows to a heightof 3 to 6 feet. The stem is branched with spinyleaves extending down the stem to give it a wingedappearance The wings are lobed and wavy witheach lobe ending in a spine. The leaves are darkbluish-green with light green midribs and have awhite margin. The-

PLUMELESS THISTLE(Carduus acanthoides L.)COMPOSITE FAMILY-CompositaeDescription: Plumeless thistle reproduces onlyby seed and grows most often as a biennial;however, it can occasionally grow as a winterannualorannual. Duringthe first yearofgrowth,a large basal rosette with a large tap root is formed.During the second year of growth, an erect floweringstem grows to a height of 3 to 6 feet. Thestemis branched and has spinywings. Theleavesare alternate, narrow, deeply lobed, have scatteredhair on the upper leaf surface, and densewhite hair on the lower surface, especially alongthe midrib. Lobes on the leaves and stem, end inwhite to yellowish spines. The flower heads areglobe-shaped, erect, single or loosely clustered,with spiny bracts at the base ofeachflower head.The flower heads are reddish-purple and1/2to 1inch in diameter. Flowering occurs from JunethroughAugust,withseedsmaturing5 to12daysafterfull bloom. Theseedsarestraw-coloredwithbrownstriations to thecollarwhere the pappus isattached. The seeds are 1/16 inch in length, usuallylinear but occasionally curved.Distribution: Plumeless thistle is primarily foundin pastures, waste areas, and along roadsides. Itprefers sandy, well-drained soils. Plumeless thistleis found throughout Minnesota.SeedlingLeafMature PlantSeed7

SeedlingLeafCANADA THISTLE(Cirsium arvense L.)COMPOSITE FAMILY - CompositaeDescription: Canada thistle is a perennial reproducingby seeds and underground roots. Theroots extend severalfeet deep and some distancehorizontally, often forming dense patches. Themature plantwill reacha heightof2 to 5 feet. Theupright stems are grooved, slightly hairy whenyoung, increasingly hairy as they mature, andbranched at the top. The leaves are alternate,have crinkled edges, spiny margins, and are somewhatlobed. The flower heads are numerous,compact, and 3/4 inch or less in diameter. Theflowers are reddish-purple to purple and are surroundedby bracts without spiny tips. Male andfemale flowers are usually borne on separateplants. Flowering occurs from June throughoutSeptember with seed maturing 8 to 12 days afterfull bloom. The seeds are gray to brown, smooth,slightly tapered, 3/16inchlong, and have a ridgearound the blossom end.Distribution: Canada thistle can be found in allcrops, pastures, waste areas, and alongroadsidesthroughoutMinnesota. Canadathistle is themostprevalent and persistent broadleaf weed in thestate.Mature PlantSeed8

FIELD BINDWEED(Convolvulus arvensis L.)MORNING GLORY FAMILY ­ConvolvulaceaeDescription: Field bindweed (also called creepingjenny or morningglory) is a perennial reproducingbybothseedsandundergroundroots.Theroot system is very extensive and may penetratethe soil to a depthof20 to 30 feet. The plant growsprostate or will climb on any nearby object. Thespreading stems are smooth, slender, usually twining,and may reach lengths of 2 to 7 feet on amature plant. The leaves are alternate with smoothmargins, and are arrow-shaped with two basallobes. The flowers are white to pink, approximately1 inchin diameter, funnel shaped, and areborne singly on long stalks in the axil of the leaf.The flower stalk has 2 bracts located 1/2 to 2inches below the flower, which helps to distinguishthis weed from hedge bindweed. Floweringoccurs from May to September. The seeds areborne in seed pods that are egg-shaped and containfour seeds. The seeds are dark brownishgray,1/8 inch long, have a roughened surface,and have one rounded and two flattened sides.Distribution: Field bindweed will grow in mostcultivatedfields, gardens, lawns,wasteareas, andalong roadsides. Field bindweed is found throughoutMinnesota, with the heaviest infestations inthe west~rn half of the state.SeedlingLeafMature PlantSeed9

LEAFY SPURGE(Euphorbia esula L.)SPURGE FAMILY - EuphorbiaceaeSeedlingFlowerDescription: Leafy spurge is a perennial that reproducesfrom both seeds and underground roots.The root system of leafy spurge is extensive andconsists ofnumerous coarse and fine roots whichoccupy a large volume of soil. Roots are mostabundantintheupperfoot ofsoil; however, somerootscanextend to a depthof15 feet ormore. Themature plantwill reach a height of 2 to 3 feet. Thestems are smooth, branched at the top, and containa milky juice (latex). The leaves are bluishgreen,linear shaped, narrow (1/4 inch wide)with smooth margins, and are alternate. Leafyspurge produces a flat-topped cluster of yellowishgreenflower-like structures called bracts onwhichthe true flowers are produced. Flowering occursfrom June through August and seeds are producedfrom July to September. The seeds areborneinseedpodswhichare3-lobed andcontain3 seeds. Theseeds are gray-white to gray-brown,usually mottled or flecked with brown, 1/8 inchin length, smooth, and on one side there is a faintdark seam that runs the length of the seed.Distribution: Leafy spurge grows primarily inpastures,wasteareas, andalongroadsides. Leafyspurge can be found throughout Minnesota.Heaviest infestations are found in the westernhalfofthestateandalongmostoftheroadsidesinMinnesota's metropolitan areas.Mature PlantSeed10

PERENNIAL SOWTHISTLE(Sonchus arvensis L.)COMPOSITE FAMILY - CompositaeDescription: Perennial sowthistle is a perennialreproducing by seed and underground roots. Rootscan penetrate the soil to a depth of several feet.The mature plant will reach a height of3 to 7 feet.The upright stems are smooth, with or withouthair, and contain a milky juice (latex). The leavesarevariable inshapeandsize. Thebasalleaves arenarrow and deeply lobed. The leaves along thestem are 4 to 8 inches long, alternate and attacheddirectly to the stem, irregularly toothed, lobed,with spiny edges. Flower heads are approximately1 1/2 inches in diameter, produced inclusters, bright yellow, and attached to terminalbranches at the top of the plant. Flowering occursin June through August and seeds mature inJulythrough September. The seeds are reddish-brown,1/8 inch in length, slightly flattened, longitudinallyribbedwith5 to 7ribs and havesmallercrosswrinkles.Distribution: Perennial sowthistle will grow incultivated fields, pastures, waste areas, and alongroadsides. Perennialsowthistleis found throughoutMinnesota with the heaviest infestations foundin the western and northern half of the state.SeedlingFlowerMature PlantSeed11

POISON IW[Toxicodendron radicans (L.) Kuntze]CASHEW FAMILY-AnacardiaceaeSeedDescription: Poison ivy is a native perennialwoodyspecies thatreproducesbybothseedsandunderground roots. Poison ivy primarily growsas a woody vine; however, if it is growing in fullsunlight it may grow as a shrubup to several feettall. As a vine, poison ivy will climb fence posts,shrubs, and trees. Older vines may be more than2 inches in diameter and may grow up to 75 feetin length. The leaves are alternate and consist of3 leaflets which can vary greatly in shape. Mostoften the leaflets are 2 to 4 inches in length,pointed at the tip, shiny, and have notched orsmooth edges. The leaves are petiolate and oftenthe terminal leaflet has the longest stem. Theflowers areyellowish-green, small, 5petaled, andborne in a cluster 1 to 3 inches long. Floweringoccurs from August through September. Not allplants will flower or bear fruit. The seeds areproduced inside a fruit which grows in clustersonslenderstemsintheaxil oftheleaves. Thefruitis grayish-white to yellow, 3/16 inchin diameterand has distinct lines marking the outer surface,somewhat like a peeled orange. The seeds aregrayish striped and approximately 1/8 inch indiameter.All parts of this plant contain a poisonous materialwhich causes blistering of the skin.Distribution: Poison ivy grows along streambanks, edges of paths and roadsides, fencerows,woodlands, and other noncultivated sites. Poisonivy prefers moist, shaded locations. Poisonivy is found throughout Minnesota, with theheaviest infestations found in wooded areas ofthe state.Fall Foliage12

PURPLE LOOSESTRIFE(Lythrum salicaria L.)and (Lvthrum virgatum L.)LOOSESTRIFE FAMILY-LythraceaeDescription: Purple loosestrife is an aquatic perennialthat reproduces by seed, underground roots,and can spread by sprouting from pieces brokenoff theplant. Ithasa woodytaprootwitha fibrousroot system that forms a dense mat. The erectstemsofa matureplantcanreach 7feet. The stemsare somewhatsquare,coveredwithfine hairs, andbranched. The leaves are opposite or whorled,linear shaped with smooth edges, hairy, and attacheddirectly to the stem. The flowers are indense terminal spikes at the top of the plant.Flowers are purple-magenta with 5 to 7 petals.Flowering begins in June and continues throughearly September. The seeds are produced in seedpods that contain many seeds. The seeds are flat,light tan to goldenbrown, and very tiny (400 x 200microns), aboutthesize ofa tip ofa pin. Eachplantcanproduce120,000 to2.7millionseedsina singlegrowing season.Distribution: Purple loosestrife is an aquaticplant that grows in wet soils in wet meadows,pasture wetlands, cattail marshes, streams andriverbanks, lakeshoresand ditches. Purpleloosestrifeinfestations are increasing in Minnesota.Currently, purple loosestrife has been identifiedin more than 75 percent of Minnesota's counties.SeedlingFlowerMature PlantSeed13

GLOSSARYalternate leaves: leaves attached singly along a stem.annual: a plant that completes its life cycle in one year or less, and reproduces only by seed.axil: point where a leaf or branch is attached to the stem.biennial: a plant that completes its life cycle in 2 years, and reproduces only by seed.bract: a modified leaf structure that surrounds the flower on some plants.leaflet: a division of the leaf.lobe: the leaf margin that is shallowly or deeply divided into sections or divisions.opposite leaves: leaves attached in pairs along the stem.pappus: a cluster of fine hairs attached to the seed in some plants, e.g., dandelion.perennial: a plant that lives for more than 2 years, and reproduces by seeds, rhizomes, orother underground plant parts.rhizome: an underground creeping stem which provides the means of production of someperennial plants.rosette: a basal cluster of leaves. The first year's growth of biennial plants.stolon: an above-ground prostrate stem which provides the means of reproduction of someperennial plants.whorled leaves: three or more leaves attached at the same point along a stem.winter annual: an annual plant that initiates growth in the fall and produces seed the followingspring.winged: any membranous extension or in some instance the extension of the leaf blade.ADDITIONAL REFERENCESThe following references on weed identification are available from theUniversity of Minnesota Extension ServiceNumberMI-1350MI-1349MI-1351MI-1352MI-2384MI-2228FO-0776TitleAnnual Broadleaf Weed IdentificationAnnual Broadleaf Weed Seedling IdentificationAnnual Grass and Perennial Weed Seedling IdentificationAnnual Grass and Perennial Weed IdentificationWeed Seedling Identification: Annual BroadleavesWeed Seedling Identification: GrassesWeed Seedling IdentificationCheck prices and orderfrom:University of Minnesota Extension ServiceDistribution CenterRoom 3 Coffey Hall1420 Eckles Ave.St. Paul, MN 55108612-625-8173Beverly R. Durgan is an extension agronomist, University ofMinnesota Extension ServiceCopy Editor: Mary Kay O'Hearn Graphic Design: Tracey J. Benson14

In addition to the ten primary noxious weeds, the Minnesota Noxious Weed Law also defines and lists 49 secondary noxious weeds.A county may select a weed or weeds from this secondary list to be placed on its noxious weeds list. Ifa secondary noxious weed isplaced on a county noxious weed list, that weed must be controlled in that county. The secondary noxious weeds are:Common NameAlyssum, hoaryArtichoke, JerusalemBuckwheat, wildBuffaloburBurdockButtercup, tallBrackenfernCarrot, wildCatchfly, nightfloweringCockle, whiteCocklebur, commonDaisy, oxeyeDock, curlyFlixweedFoxtail, giantGumweedHawksbeard, narrowleafHawksbeard, smoothHawkweed, orangeJimsonweedKnapweed, spottedKochiaLambsquarters, commonMallow, veniceMarshelderMilkweed, commonMuhly, wiresternMustard, wildNightshade, eastern blackNutsedge, yellow (nutgrass)Oat, wildPanicum, fallPanicum, wild proso milletPigweed, redrootPigweed, prostrateQuackgrassRadish, wildRagweed, commonRagweed, giantSandbur, fieldSmartweed, PennsylvaniaSmartweed, (ladysthumb)Sorghum-almumSunflower, common (except cultivars)TansyVelvetleafYellow rocketWoolly cupgrassWormwood, absinthGenus and speciesBerteroa incanaHelianthus tuberosusPolygonum convolvulusSolanum rostratumArctium minusRanunculus acrisPteridium aquilinumDaucus carotaSilene noctifloraLychnis albaXanthium pensylvanicumChrysanthemum leucanthemumRumex crispusDescurainia sophiaSeteria faberiiGrindelia squarossaCrepis tectorumCrepis capillarisHieracium aurantiacumDatura stramoniumCentaurea maculosaKochia scopariaChenopodium albumHibiscus trionumIva xanthifoliaAsclepias syriacaMuhlenbergia frondosaBrassica kaberSolanum nigrumCyperus esculentusAvenafatuaPanicum dichotomiflorumPanicum miliaceumAmaranthus retroflexusAmaranthus blitoidesAgropyron repensRaphanus raphanistrumAmbrosia artemisiifoliaAmbrosia trifidaCenchrus pauciflorusPolygonum pensylvanicumPolygonum persicariaSorghum almumHelianthus annuusTanacetum vulgareAbutilon theophrastiBarbarea vulgarisEriochloa villosaArtemisia absinthiumAdditional information on the laws governing, and on the enforcement of the noxious weed law can be obtained from:Minnesota Department ofAgriculture, Agronomy Division Section ofWeed Control,90 West Plate Boulevard, St. Paul, MN 55107 Phone: 612-296-612315

FO-5620-SReviewed 1998www.extension.umn.eduCopyright © 1998, Regents of the University of Minnesota. All rights reserved.For ordering information call 612-625-8173.Produced by Communication and Educational Technology Services, University of Minnesota Extension Service.The information given in this publication is for educational purposes only. References to commercial products or trade names is made withthe understanding that no discrimination is intended and no endorsement by the University of Minnesota Extension Service is impliedFor Americans with Disabilities Act accommodations, please call (612) 625-8173.The University of Minnesota Extension Service is an equal opportunity educator and employer.Printed on recycled paper with minimum 10% postconsumer waste.