Cold Hardy Citrus

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Title:
Cold Hardy Citrus
Physical Description:
Fact sheet
Creator:
Jackson, L.K.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:

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Acquisition:
Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"Publication date: June 1992. Revised: June 1994."
General Note:
"HS-123"

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Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the submitter.
System ID:
IR00004624:00001


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FactSheetHS-123 June1994ColdHardyCitrus1 L.K.JacksonandT.R.Fasulo2Thehomecitrusgrowerisatadistinct disadvantagetryingtogrowcitrusinnorthandwest Floridasinceitwillfreezeinmostyears.Sincecitrus speciesarebasicallysubtropicalortropicalcropsthey willnottoleratemosttemperaturesbelow28F.The homefruitgrowercannotcontroltheclimate,but therearecertainotherfactorshecanchangewhich willinfluencethechancesofsurvivalofacitrustree innorthandwestFlorida.Moreover,thereare severalstepshecantaketomodifytheimmediate micro-climateofacitrustreeandthusenableitto withstandfreezingtemperatures.COLDHARDYVARIETYSELECTIONSTrifoliateorange(aninediblecitrusrelative)can withstandthelowesttemperatureofallcitruswhenit ismatureandfullydormant,followedbykumquat, satsuma,calamondin,sourorange,mandarin,sweet orange,grapefruit,shaddock,lemon,limeandcitron. Grapefruit,shaddock,lemon,limeandcitronarenot recommendedoutsidethecommercialcitrusbeltof Florida.Somesweetoranges,somemandarinsand calamondinhavesufficientcold-hardinesstobegrown northofthecommercialcitrusbelt,butsouthofa linedrawnfromthemouthoftheSuwanneeRiver throughGainesvilletoGreenCoveSpringsandthen uptheSt.JohnsRivertotheocean.Theycanbe successfullygrowninthisareainmostyears.Specific citrustypeswhichcanbegrownintheareadescribed aboveinclude:SweetOrange,Mandarin,Calamondin, Satsuma,Kumquats.Themostprominentcitrusfruit whicharesufficientlycold-hardytogrowthroughout northandwestFloridaaresatsumaandkumquats.COLDHARDYSWEETORANGESVarietiesofsweetoranges( Citrussinenesis (L.) Osbeck)whichcanbegrowninthisareaarenavels, Hamlin,andParsonBrown.Theseorangesmaturein theearlytolatefallsothatfreshfruitwouldnormally beharvestedbeforeaseverefreezewouldbe expected.Thepreferredrootstockistrifoliateorange formaximumcold-hardiness,withsourorangebeing secondchoiceiftrifoliateorangeisnotavailable. Swinglecitrumeloisanothergoodrootstockformost ofthisarea.Oneothernewvarietywhichcouldbe consideredisAmbersweetwhichisclassifiedasan orangealthoughitisactuallyahybrid. 1.ThisdocumentisFactSheetHS-123,aseriesoftheDepartmentofHorticulturalSciences,FloridaCooperativeExtensionService, InstituteofFoodandAgriculturalSciences,UniversityofFlorida.Publicationdate:June1992.Revised:June1994. 2.LarryK.Jackson,professor,extensionhorticulturist,DepartmentofHorticulturalSciences,CitrusResearchandEducationCenter (CREC),LakeAlfred,Florida,abranchcampusoftheUniversityofFlorida,Gainesville,Florida;ThomasR.Fasulo,associatein entomology,entomologist,DepartmentofEntomologyandNematology,CooperativeExtensionService,InstituteofFoodandAgricultural Sciences,UniversityofFlorida,GainesvilleFL32611. Theuseoftradenamesinthispublicationissolelyforthepurposeofprovidingspecificinformation.Itisnotaguaranteeorwarrantyofthe productsnamed,anddoesnotsignifythattheyareapprovedtotheexclusionofothersofsuitablecomposition. Theterm"plates,"whereusedinthisdocument,referstocolorphotographsthatcanbedisplayedonscreenfromCD-ROM.These photographsarenotincludedintheprinteddocument. TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/ChristineTaylorStephens,Dean

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ColdHardyCitrus Page2COLDHARDYMANDARINSThemandarins(Citrusreticulata Blanco)and mandarinhybridsforthisareaincludeDancy tangerine,Orlandotangelo,Robinsontangerineand Sunburst.Thepreferredrootstockforcold-hardiness istrifoliateorange,butsourorangeorCleopatrawill beeasiertofind.Changshamandarinisquitehardy withfairquality,butmaybedifficulttolocate.COLDHARDYSATSUMASatsumaisthemostcold-tolerantofcommercial citrus,withmature,dormanttreeshavingsurvived15 Fwithoutseriousinjury.Consequently,itisadapted toregionsthataretoocoldformostothercitrus,as ithasnotprovencommerciallyacceptableinmilder regionsofthesubtropics. Thesatsumatreeismoderatelyvigorous, medium-small,veryproductiveandmarkedly cold-resistant.Greatestcold-hardinessisattainedon trifoliateorangerootstock,whichalsocausesdwarfing ofthetree.COLDHARDYKUMQUATSKumquatsexceedevensatsumaintermsof cold-hardiness,beingabletosustain10Fwhenfully dormant.Activegrowthoccursonlyatrelativelyhigh temperatures,sotheplantsremainsemi-dormant duringlatefall,winterandearlyspringinwarm temperateclimates.Theynormallybloomlongafter citrusandceaseactivegrowthearlierinthefall, whichcontributestotheircold-hardiness. Trifoliateorangeisthepreferredrootstockfor kumquatsgrownincoldregions,whichfurther reducestreesize.PLANTINGSITEColdairdrainsdownhill,sohigherelevationswill besomewhatwarmerthanthesitesatthebottomof ahillorslope.Usually,thesouthandsoutheastsides ofalakeorotherbodyofwaterwillbewarmerthan thenorthsideorsiteswithnowaternearby.Planting onaslopeorsouthofabodyofwateraffordssome coldprotection.Theaverageresidentiallotdoesnot normallypermitsuchconsiderations,however. Plantingonthesouthsideofandatthecorrect distancefromthehousewillbehelpful.Mostfreezes andwinddriftarefromthenorthandnorthwest,thus thehousewillactasawindbreak,forcingthecoldair upandoveritandthecitrustrees,leavingthearea nearthesouthsidesomewhatwarmer.Thehouse itselfradiatesconsiderableheat,someofwhichwill beabsorbedbyadjacentplants,thuswarmingthem.CULTURALPRACTICESThesoilunderandaroundacitrustreeshouldbe completelyfreeofweeds,grassormulchduringthe winter.Grassormulchonthesoilactsasan insulator,hencesolarheatispreventedfromentering thesoilduringthedayandlessheatisstoredfor releasefromthesoilatnight.Acleanpackedsurface allowsmaximumheatabsorptionduringthedayand maximumheatradiationatnight.Moreover,moist soilwillabsorbmoreheatthandrysoil,sotrees shouldbethoroughlywateredjustdaysbeforeabad freezeispredicted.Finally,goodtreehealthand nutritionwillhelpthetreewithstandfreezing temperatures. Followrecommendedculturalpracticesand fertilizationtomaintainthetreesinthebest condition.Fertilization,sprayingandpruningshould endinSeptemberinordertoallowthetreesto hardenoffcompletelybeforeseverefreezesare encountered.COLDPROTECTIONDooryardfruitgrowersmustprovideadditional coldprotectiontothetreesduringseverefreezes. Youngcitrustreesshouldbebanked(Plate1)forthe first3-5wintersuntilthetreeislargeenoughto withstandcold. Analternativetobankingistheuseoftreewraps (Plate2).Additionally,treesmaybecovered temporarilywithblankets,quilts,paperorother materialasfurtherprotectionagainsthardfreezes. However,suchmaterialshouldberemovedeach morningtoallowthetreetotakefulladvantageof incomingsolarradiation. Irrigationmayalsobeusedforcoldprotection butisnotwithoutrisk.Ifwatersuppliesare interruptedforanyreasontreesprotectedwithwater maysuffermorethanothertreeswhichwere unprotected.Whendependablemunicipalwateris available,thecombinationofirrigationjudiciously appliedtothelowerportionofthetreeplus insulatingwrapsonthetrunkmayprovidegood protection.