Cappaioicn

THEBIOLOGYOFCANADIANWEEDS.
21.
UrticadioicqL.
l.
J.
BASSETT',C.
W.
CROMPTON1,andD.
W.
WOODLAND'zIBiosystematicsResearchInstitute,AgricultureCanado,Ottawa,OntarioKlA0C6;and2DepartmentofPlantSt:iences,MacdonaldCampusofMcGillUniversity,Ste.
AnnedeBellevue,QuebecH9AlC0Receivedl5Sept.
1976,acceptedl3Ocr.
1976.
Besse'rr,I.
J.
,CnovproN,C.
W.
ANDWooDLAND,D.
W.
1977.
ThebiologyofCanadianweeds.
2l.
Urticadioit:aL.
Can.
J.
PlantSci.
57:491-498.
AsummaryofbiologicalinformationonUrticadioicaL.
ssp.
gracills(Ait.
)Sefander(Americanstingingnettle)andssp.
dioica(Europeanstingingnettle)ispresented.
AmericanstingingnettleiswidespreadthroughoutCanada,whileEuropeanstingingnettleisconfinedtoafewdisturbedhabitatsinEasternCanada.
Americanstingingnettleisoftenweedyinnutrient-richsoilssuchasarenormallyassociatedwithcultivatedrowcrops,oldpastures,farmyards,irrigationcanals,drainageditches,orchards,andopenwoodlands.
AirbornepollenofUrticadioica,shedinlargeamounts,inknowntocausehayfever.
Thestingingemergences(needles)ofbothsubspeciesproduceapainfulstingtothehumanflesh.
L'auteurprdsentedesdonndesbiologiquessurUrticadbicaL.
ssp.
gracilis(Ait.
)Selander(ortiedioiqued'Am6rique)eIssp.
dioicn(ortiedioiqued'Europe).
Lapremibreestr6pandueauCanadaalorsquelasecondeselimitehquelqueshabitatsd6rang6sdeI'estduCanada.
L'ortied'Am6riqueestsouventunemauvaiseherbedessolsfertiles,telsceuxquisontnormalementassoci6sauxculturessarcl6es,vieuxpAturages,coursdeferme,canauxd'irrigation,foss6sdedrainage,vergersetbois6sclairs.
OnsaitquedegrandesquantitdsdepollenensuspensiondansI'aircausentlafibvredesfoins.
Lespoilsurticantsdesdeuxsous-espdcescausentdespiq0resdouloureuseshl'homme.
l.
NamesUrticadioicaL.
-stingingnettle(CanadaWeedCommittee1969);ortiedioique,ortie,ortiepiquante(FerronetCayouette1971).
TwosubspeciesoccurinCanada:l.
thecommonandwidespreadnativetaxon,U.
dioicassp.
gracilis(Ait.
)Selander-Americanstingingnettle,ortiedioiqued'Am6rique2.
therareintroducedtaxon,U.
dioicaL.
ssp.
dictica-Europeanstingingnettle,ortiedioiqueduEurope.
Urticaceae,nettlefamily,Urticac6es.
2.
DescriptionandAccountofVariationUrticadioicassp.
gracilis.
Erectorpar-tiallyascendingperennialswithextensiverhizomesystem;stems(0.
5)l-2(2.
5)mtall,slender,simpleorwithaxillarybranches,glabrous,exceptforstingingCan.
J.
PfantSci.
57:491-498(Apr,1977)emergences,toslightlypilose,hispidorstrigose;stipules5-12mmlong,free,oblongtolinear-lanceolate,acutetoat-tenuate;leavesopposite,broadlyovatetolanceolate,roundedtocordateatbase,acutetoacuminateattip;petiolesslender(l18)ll4-213thelengthoftheblade,longeronlowerstemleaves,shorteronupperleaves;bladesglabrousonbothsurfacestosparinglypiloseorstrigosebeneath,coarselyserratetodentate;cystolithsrounded;teethdirectedforward,l-5mmdeep,thoseoflowerbladeslarger,upperbladessmaller;plantspredominantlymonoecious,rarelydioecious;staminateflowerclustersgenerallyequaltoorlongerthanthepetioles,greenishyellowwithfourequalsepalsandfourstamens;pistillateflowerclustersgenerallyshorterthanthepetioles;innersepalsovate,slightlyto491192CANADIANJOURNALOFPLANTSCIENCEmoderatelyhispid,(0.
5)1.
0-1.
5(2.
0)mmlong;outersepallobesonmatureflowersgenerallyll4-l12(2/3)longerthantheinnerlobes;achenes1.
0-|.
5mmlong,ovate,tantobrown,smoothtotuberculate;wind-pollinated,floweringfrornlateMaytoOctober.
ThecommonAmericanstingingnettle(ssp.
gracilis)canbedistinguishedfromtheinfrequentEuropeanstingingnettle(ssp.
dioicabythefeaturesdetailedinthefollowingkey:Plantspredominantlymonoecious(pistillateplantsoccasional,staminateonesrare);stemsrigid,theplantsuprightinhabit;leafbladesandstemsglabrouswithstinginghairsusuallyonlowerleafsurfaceonlyU.
dktic'assp.
grac'ilisPlantspredominantlydioecious;stemsweak,theplantswithasprawling,branchinghabit;leafbladesandstemsusuallystronglyhispidwithstingingl1'::::1':'::i:::',i:;"i,,,,pai.
ii,Chromosomenumbersof2n:26and2n:52havebeenreportedforssp.
gracilisand2n:52forssp.
dioicabyBassettetal.
(1914).
StingingnettleissometimesconfusedwithBoehmeriacylindrica(L.
)Sm.
(boghemp),GaleopsistetrahitL.
(hempnettle)andVerbenaurticifoliaL.
(whitevervain).
However,theseplantslackthestinginghairsthatarepresentonstingingnettlefromthetwo-leafstageonwards.
SeedfingsandfloweringshootsofUrticadioicassp.
gracilisareillustratedinFigs.
Iand2.
Theseedlingsofssp.
dioicaaresimifartothoseofssp.
gracilis.
Fi-c.
l.
Sccdlings.
Fig.
2FloweringshootBASSEIEIAI.
-URTI('ADIOICAL4933.
EconomicImportance(a)Detrimental-MajorinfestationsofAmericanstingingnettlehavebeenob-servedinorchards,marketgardens,farmyards,nurseries,oldpastures,alongroad-sides,drainageditches,irrigationcanalsandstreambanksinthesouthernportionofitsCanadianrange.
Thestingingemergencesonthestem,leavesandflowersofstingingnettleplantsproduceapainfulstingtothehumanflesh,followedbyanimmediatesmallreddishswellingandprolongeditchingandnumbnessofthesensitizedarea.
Initialreactionslastafewminutesonfirstbeingexposed.
Afterbeingstungrepeatedly,thepainoftenintensifiesandcanlastforseveraldays.
ThepollenofAmericanstingingnettle,shedinlargeamounts,isanimportantcontributortosummerhayfever.
SolomonandCathey(19'70)tested84atopicpatientsepidermallywithextractsofAmericanstingingnettlepollen.
Ofthepatientstested,20Vodevelopedallergenicreactionsexceedingtheirresponsetoextractsofcommonragweed(AmbrosiaartemisiifoliaL.
).
A32-yranalysisofatmosphericpolleninMinnesotarankedUrticaspp.
lOthinabundanceamong50plantgenera(HansenandDahl1965).
(b)BeneficialFernaldandKinseY(1958),andWoodland(1973)reportthatyoungAmericanstingingnettleleavesmakeanexcellentpotherb,andcanbeboiledandsubstitutedforspinach.
TheytelloftheuseoftheEuropeanstingingnettleinScotlandinearliertimesasarennettocurdlemilkforcheese.
InGermany,duringWorldWarII,theEuropeanstingingnettlewasgatheredasfoodforhumanconsump-tionbecauseofitshighnutritivevalue(Stern1943).
InRussia,nettlehaywastestedagronomicallyandfoundveryhighinproteinandlowinfibre,andproducedhighyieldonthesecondandthirdcuttings(Totev1964).
Cappa(1965),inItaly,comparedthenutritivevaluesofnettlemealversusalfalfamealonpulletsandhens.
Thebirdsfedonnettlemealreachedsexualmaturityearlierandproducedmoreeggsperbirdthanbirdsfedonalfalfameal.
Europeanstingingnettleissometimesusedbyforestersasanindicatorofsoilssuitableforreforestation,sincenettlesgrowmainlyinareaswithhighsoilfertility(Pigort1964).
(c)Legislation-Americanstingingnettle(U.
dioicassp.
gracilis),underthenametallnettle,isincludedinthelistofnoxiousweedsforManitoba(Anonymousl97O),andunderthenameUrticadioica(sensuIat.
)isdesignatedanoxiousweedbytheProvinceofAlberta(Anonymous1973).
4.
GeographicalDistributionAmericanstingingnettleoccursinallprovincesaswellastheYukonTerritory,andMackenzieDistrict,N.
W.
T.
(Fig.
3).
Althoughwideranging,thisplantisabun-dantmainlyinlowlandsituationsandisoftenassociatedwithhumanhabitation'Infestationsarefoundinrichsoilssuitedformarketgardens,nurseries,andorchards.
ThedistributionofAmericanstingingnettleextendssouthtoVirginia,Missouri,Louisiana,northernTexas,NewMexico,easternUtah,Arizona,andCalifornia'Europeanstingingnettle(Fig.
3)iscos-mopolitanintemperateregions(Wood-land1975).
5.
Habitat(a)Climaticrequirements-WithinCanada,AmericanstingingnettleoccursfromtheUnitedStatesbordernorthto62"latitudeinthewest,andnorlhto53'latitudeintheeast.
AsindicatedbythisextensivedistributionandthecollectingsitesshowninFig.
3,variousamountsofrainfallandsnowcoveraretoleratedbythistaxon'Americanstingingnettlewillgrow(basedon42"F)fromunder600-800degree-daysintheforesttundrato3,250degree-daysintheGreatLakes-St.
Lawrenceforestreg-ions(Rousseau1974),(b)Substraturz-Woodland(1975)sam-pledsoilfrom38Americanstingingnettle494CANADIANJOURNALOFPLANTSCIENCEFig.
3.
DistributionofAmericanstingingnetrle(IJrticadioicassp.
gracilis),andEuropeanstingingnettfe(U.
dioicassp.
dioica)inCanada.
populationsintheUnitedStates.
ThepHofthesesamplesrangedfrom5.
6to7.
6onsiteswestoftheRockyMountainsandfrom6.
2to7.
5onmoreeasternsites.
InCanada,AmericanstingingnettlegrowsinPodzol,Brunisol,HumicGleysolic,Gleysolic,andCyricGleysolsoils.
Itgrowsmorecommonlyonpodzoland_Brunisolsoiltypeswhereleachingtendstocauserapidbreakdownonanyaccumulatingorganicmatter.
(c)Communitiesinwhichthespeciesoccurs-AmericanstingingnettlegrowsineightoftheninebioclimaticzonesinQuebecdefinedbyRousseau(1974).
Thesezonesrangefromforest-tundraassociationstoGreatLakes-St.
LawrenceForestassoci-ations.
Americanstingingnettleisrarelyobservedasasingleplantwithoneorafewstems.
Itusuallyformsinlargeclosedclones.
Thelargestinfestationsseenonrecentcross-Canadafieldsurveysforsting-ingnettlewerealongtheSt.
JohnRivei,N.
B.
,inmarketgardenareassouthofMontrealandalongdrainageditchesandinorchardsoftheeasterntownships,euebecandsouthernOntario.
AlargepopulationofAmericanstingingnettleextendsforl5kmalongthehighwayembankmentbetweenKenora,OntarioandWinnipeg,Manitoba.
Itisalsocommonincouleesandalongstreambanksontheprairies,andontheperipheryoforchardirrigationrun-offintheOkanaganValley,B.
C.
6.
HistoryAmericanstingingnettleisundoubtedlynativetoNorthAmerica.
AnUpperCre-taceousfossilresemblingAmericansting-ingnettlewasfoundinAlaska(HollickandMartin1930).
ItisconsideredbyMcAn-drewsetal.
(1973)toformaportionoftheQuaternaryfloraoftheGreatLakesRegion.
AftertheWisconsinglaciation,itevidentlymigratednorthwardintoCanadaduringtheHolocene.
Cushing(1963)foundfossilUrtica-typepolleninMinnesotaborings,radiocarbon-datedfrom7,800B.
P.
untilrecenttimes.
WehaveidentifiedUrticapolleninHolocenesedimentsamples7,600-8,100B.
P.
and8.
600-9,100B.
P.
fromsouthernOntaro(radiocarbondatesBASSE1EIAL.
-URTICADIOICAL.
49sprovidedbytheGeologicalSurveyofCanada).
Theearliestbotanicalcollectionofthistaxonwasmadein1189atHudsonBay(Bassettetal.
1974).
TheoldestcollectionoftheintroducedEuropeanstingingnettleisfromStoneMills,BayofQuinte,Ontario,whereitwasfirstfoundin187'7byJ.
Macoun.
IthassincebeencollectedinscatteredlocationsinEasternCanada.
Itisusuallyfoundnearports,ballastheaps,andrailwayyards.
7.
GrowthandDevelopment(a)Morphology-TheweedinessofAmericanstingingnettlecanbeattributedtothevigorousspreadoftheplantby*eansofrhizomes.
Therhizomescanestablishnewcoloniesfromwhichotherspeciesarevirtuallyexcluded,whenscatteredthroughthesoilbydisturbancessuchasmechanicalcultivation.
Stingingemergencesalsocausemantoavoidhand-weedinssmallerinfesta-tions.
(b)Perennation-Americanstingingnettleiskilledbacktogroundlevelbyfrosteachyear.
Itsurvivesinthesoilthroughitsperennatingrhizomes.
(c)PhysiologicaldataBecauseofnettle'sinjurioussting,thephysiologyandchemistryofitsemergenceshavebeenstudiedextensively.
Willis(1969),usinggas-phasechromatography,thin-layerchromatography,andelementalanalysiswasunabletodeterminethechemicalconstitutionofthetoxin.
Hedisprovedtheresultsofmanypreviousauthorswhohadtentativelyidentifiedthetoxinsasacids,alkaloids,enzymes,histamines,saltsandproteins.
Thecausativeagentofthenettles'stingstillremainsunknown.
Americanstingingnettlewillnotpersistinareaswhicharesaline,orinhabitatsoflowsoilfertility.
Rorison(1967)discoveredthatcalciumreducedthepermeabilityofUrticarootcellstophosphorus.
Lowphosphatelevelsresultedinslowgrowthrates;highphosphatelevelsresultedinfastgrowthrates.
Nassery(1970)determinedthatlackinganabundantsupplyofphos-phate,Urticawillshowdeficiencysymptomsandgrowpoorly.
Totev(1964)analyzedthechemicalcompositionofUrticahay.
Thishaycontained2l-23%ocrudeprotein,3to5Eocrudefats,35-39Vonon-nitrogenextractsubstances,9-2l%ocrudefibreandl9-29%oash.
Cappa(1965)foundthattheaminoacidscontainedindehydratedmealofUrticadioicawerenutritionallysuperiortotheaminoacidconcentrationsofdehydratedalfalfameal.
(d)Phenology-Duetoitswidegeo-graphicalrange,thephenologyofAmericanstingingnettleissomewhatvariable.
Maximumrootdevelopmentoccursinthelatespringandearlysummer,priortofloweringandsubsequentseedsetting.
AmericanstingingnettleflowersfromlateMaytoearlyOctober.
Ontheprairiesandinthenorthernareas,floweringiscondensedintotheperiodfrommid-JunetolateAugust.
Noseedlingshavebeenobservedinthefield.
8.
Reproduction(a)Floralbiology-Americanstingingnettleisanemophilous.
Asthestaminateflowersmature,theanthersdehisceforcingtheperianthpartstoopen.
Meanwhile,thefilamentswhicharebentspring-like,re-lease,andthepollengrainsarecatapultedfromtheopenanthersintotheair.
Wehaveseenthepollengrainsthrownupto2cmfromtheflower.
Americanstingingnettleismonoecious,bearingstaminateandpistillateflowersoneachshoot.
Somepaniclesareentirelymale,someentirelyfemale,andsomearemixed(occasionallyhermaphroditicflowersareproduced).
MaleflowersareproducedingreaterabundanceduringJuneandJulyandfemaleflowersmostlylaterinthegrowingseason.
Thishasledtothemistakenviewthattheplantsaredioecious.
Americanstingingnettleisself-compatible;pistillateflowersbaggedto-eetherwithstaminateflowersofthesame496CANADIANJOURNALOFPLANTSCIENCEplantingreenhouseexperimentsproduceviableseed.
(b)SeedproductionanddispersalAmericanstingingnettleproducesoneacheneperflower.
Theflowersarearrangedinfourbranchingpaniclesatthenodes,betweenthepetioleandshoot.
Eachclusteroffourpaniclesproducesapproximately1,000seeds.
Plantsgrowingintheshadehaveloose,drooping,panicleswith500-5,000seedspershoot,whereasopengrownplantshavecompactstiffpaniclesthataremuchmoreproductive,with10,000-20,000seedspershoot.
SomeAmericanstingingnettleclonesundoubtedlyproducebillionsofseeds.
Theachenesnormallyremainontheplantuntilfrost,whentheyfalltotheground.
Someremainontheplantuntiltheyareremovedbysnowfallandice.
(c)Viabilityofseedsandgermination-Americanstingingnettleseedsrequirenovernalization.
Seedcollecteddirectlyfromaplantwillgerminatein5-10days.
Seedswillgerminateinthegreenhouseafterl0yrstorage.
(d)Vegetativereproduction-Americanstingingnettlesurvivesthroughvegetativereproductionbyrhizomes.
Plantsestab-lishedfromseedintestsituationsinitiatevegetativespreadinthefirstgrowingseason.
Arhizomeplantedinthelatersummercanspreadto2.
5mindiameterbythefollowingyear.
9.
HybridsTheonlyotherUrticasp.
inCanadaisU.
urensL.
ThereisnoevidencethatU.
dioicahybridizeswithit.
theplantcouldestablishitselffromseedwhenplantedintoherbageandforagetestplots.
Nettlebecamethedominantweedinlegumemixtures,waslessdominantinlegume-grassmixtures,andwasconsider-ablyreducedinpuregrassplots.
FieldobservationsofAmericanstingingnettleinCanadaindicatethatcompetitionfromgrassspecieslimitsthespreadofnettleclones.
ThefactorspreventingAmericanstingingnettlefrombecomingmorewidespreadandabundantare:poorsoilconditions,competi-tionfromsoilbindingplants,shadefromforesttrees,andthehighmortalityofseedlings.
Severalcollectingsitesof25yragowererevisitedtofindtheinfestationstillprevalent.
Aconservativeestimateoftheageofsomenettlecloneswouldbeatleast50yr.
11.
ResponsetoHerbicidesandotherChemicalsAsthereisnospecificallyrecommendedchemicalcontrolforAmericanstingingnettleinCanada,generalcontrolrecom-mendationsforperennialweedsinnon-croplandwillprobablyeradicatethisplant(Anonymous1975).
12.
ResponsetoOtherHumanManipulationsThreesmallclosedclonesofAmericanstingingnettlewerecutclosetothegroundon5July1974,nearOttawa,Ontario.
Theplantrespondedtothiscuttingbysendingupnumerousbushyshoots.
Totev(1964)foundthatahigherpercentageyieldofEuropeanstingingnettlewasobtainedonthirdcuttingforhay.
Americanstingingnettlewillnotsurvive10.
PopulationDynamicsrepeatedploughingandmechanicalcultiva-InCanada,Americanstingingnettleisution.
Severalyearsofsuchpracticeswillminorconstituentofwoodlandclearings,effectivelyreduceinfestationbydestroyingstreamalluviums,couleesandopenrange.
itsextensiverhizomesystem(MuenscherUponopeninglandforagriculturalde-1955).
velopment,theplantestablishesitselfinareasofhighsoilfertilityandbecomes13.
ResponsestoParasitesweedy.
IntestswithEuropeanstinging(a)Insectsandothernondomesticstock-nettleinBritain,Ivins(1952)provedthatSenandJensen(1969)'reportthat(lrticaBASSETETAL.
-URTICADIOICAL497spp.
arethepredominatehostsforthehopcystnematode,HeteroderahumuliFilipjev.
Vegetables,foragecrops,fruits.
andcerealsinCanadaareinfectedbythisnematode.
Beirne(1972)discussedtheoccurrenceoftwo-spottedspidermite,TetranychusurticaeKoch,andoftheblg,CalocarisnorvegicusGmel.
onUrticadioica.
Theformerisresistanttoinsecticidesandmovesfromthehosttoinfestvegetables,clover(Trifoliumspp.
),andgreenhouseplants.
Thelatterhasbeenfoundonstrawberries(Fragariaspp.
)andpotatoes(SolanumtuberosumL.
)inNewfoundland.
Davis(197I)lists28speciesofinsectsconfinedtoEuropeanstingingnettleandafurtherl8speciesforwhichitisanimportanthost.
Hedescribesthepartsoftheplantwhichareattackedbythevariousstagesoftheinsects.
Morerecently,Davis(1973)hasreportedontheHemipteraandColeopterafoundontheEuropeanstingingnettleinEngland.
OtherinsectsfoundassociatedwithAmericanstingingnettleinCanadaareasfollows(J.
E.
H.
Martin,personalcom-munication):VanessaatalantaL.
,Bolariasp.
,PolygoniainterrogationisFabricus,P.
comaHarrts.
P.
satyrusEdwards.
Nvm-phatismilbertiLairielle(Lepidoptira:Nymphafidae);MelagromyzamartiniSpencer,PhytomyzaflavicornisFall.
,Ag-romyzapseudorystansNow.
,A.
reptansFall.
(Diptera:Agromyzidae,fromSpencer(r969)).
(b)Micro-organismsandviruses-Con-ners(1967)referstothefollowingfungibeingfoundonAmericanstingingnettle:Dendryphiumvinosum(Berk.
andCurt.
)Hughes(HelminthosporiumutricaePk.
),DidymellaeupyrinaSacc.
,Leptosphaeriaacuta(Moug.
)Karst,L.
doliolum(Pers.
)deNot.
,PistillariamicansPers.
exFr.
,PuccinicaricinaDC.
(P.
caris(Schum.
)Schroet.
varurticata(Kern)Arth.
),RamulariaurticaeCes.
,Sclerotiniasclerotiarum(Lib.
)deBary,Septoriaur-ticaeDesm.
'InadditionD.
B.
O.
Savile(personalcommunication)reportsthatpowderymil-dew(ErysiphecichoraccarumDC.
exM6rat),downymildew(Peronosporaur-ticae(Lib.
)deBary),andarustalternatingtoCarexspp.
(PucciniaurticataKernOI)havebeenfoundonAmericanstingingnettle.
Thesefungiseldomcauseseveredamagetotheplant.
(c)Higherplantparasites-Doder(Cas-cutaspp.
)occasionallyparasitizesAmeri-canstingingnettleinOntario.
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