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Growth Regulators for Containerized Herbaceous Perennial Plants

A Guide to Growing Top-Quality Perennials By Joyce G. Latimer, Department of Horticulture, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

A GUIDE TO GROWING TOP-QUALITY PERENNIALS | GROWERTALKS

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CONFORMITY: TheKeytoHigherPerennialProfits

EDITORIAL

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oday,ittakesconsistent size,shapeandqualityto increaseperennialprofits. That’swhymoreand moretopgrowersare turningtotheonecompanythatfocusesallofitseffortsonhelpingyou conformtomarketdemands—Fine Americas. Only Fine Americas offers you so much in every product.

AsaleaderinPGRresearchanddevelopment,FineAmericasisdedicatedto offeringyoueverythingyoulookforina trustedsupplier: • One-of-a-kind products— FineAmericasistheonlycompanyto offerapure2%6-BAplantgrowthregulatorforornamentals—Configure. • Advanced formulations— In2011,FineAmericasintroducedthe world’sfirstandonly4%paclobutrazol formulation—Piccolo10XC. • Uncompromising quality control— EveryPGRsoldbyFineAmericasis manufacturedunderISO9001-2008 standards,themoststringentquality controlstandardsintheindustry. • Ongoing university support— BeforeFineAmericasbringsanew PGRtomarket,wemakesureit passesthetoughesttestsatthenation’sleadingornamentalresearchuniversities.Thenweworkhand-in-hand withuniversityresearcherstoaddeven morevaluetoourproductlinethrough ongoinglabelexpansion. • Top-notch technical support— ServiceafterthesaleissomethingFine Americastakesveryseriously.That’s whyweofferoutstandingtechnical

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supportfromourtechnicalservicesdepartment,aswellasourregionalsales managers. • Nationwide distribution— FinePGRsareavailablefromleading distributorsintheU.S.andCanada. Foradistributornearestyou,goto www.fine-americas.comorcall888474-FINE(3463). • Unbeatable value— FinePGRsarepricedrighttoofferyou outstandingperformanceatareasonableprice. Continuing our commitment to grower education. FineAmericas’sponsorshipofthenew GrowerTalks PerennialsPGRGuideis justthelatestexampleofourcommitmenttogrowereducation.Wehope youfindthisinformativepublicationa valuableadditiontoyourreferencelibraryandwelookforwardtoworking withyouinthefuture.

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2012 PGR GUIDE ManagingGrowthofHerbaceousPerennialPlants BYJOYCELATIMER,VIRGINIATECH

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PGRs.Researchyourcrop,includingits responsivenesstoPGRs.

hereisatremendousdiversityof herbaceousperennialplant speciesbeinggrownforboththe retailandlandscapingsectorsoftheindustry.Growthregulationofthesecontainerizedplantsisofparticularconcern.In productionsettings,aswellasinretaillocations,herbaceousperennialsgrownin potstendtostretchandbecomeleggyor simplyovergrowtheirpotsbeforetheir scheduledmarketdate.Theseplantsare lessmarketableandhardertomaintain.

Plantgrowthregulators(PGRs)arechemicalsthataredesignedtoaffectplant growthand/ordevelopment.Mostofthe PGRsusedinthegreenhouseornursery areusedtoregulateshootgrowthofcontainerizedcropsbyinhibitingtheproductionofgibberellins—theprimaryplant hormonesresponsibleforcellelongation. Therefore,thesegrowthretardanteffects areprimarilyseeninstem,petioleand flowerstalktissues.Lessereffectsare seeninreductionsofleafexpansion,resultinginthickerleaveswithdarkergreen color.Plantgrowthretardantsalsoincreasethetoleranceofplantstotemperatureanddroughtstress,aswellastothe stressesofshippingandhandling,thereby improvingshelflifeandextendingplant marketability.Otherbenefitsofusingthese PGRsinplantproductionincludeimprovedplantappearancebymaintaining plantsizeandshapeinproportionwiththe pot,andincreasedshippingcapacitywith thesmallerplants. AlthoughthereismuchscientificinformationonusingPGRsonornamentalplants, it’snotanexactscience.Achievingthe bestresultswithPGRsisacombinationof artandscience—sciencetemperedwitha lotoftrialanderror,andagoodunder-

Start thinking about growth control early, especially for the application of PGRs.

standingofplantgrowthanddevelopment underyourenvironmentalandproduction conditions. Integrated growth regulatIon

Forbestresults,PGRsshouldbehandled asproductiontools,likewaterandfertilizer.PGRsshouldbeanintegratedpartof yourcropproductioncycle,usedinconjunctionwithanumberofnon-chemical controloptionstomanipulateplant growth,sowell-proportioned,compact plantsareproduced.Selectingshorter growingcultivarsisoftenthefirststep availabletogrowersforreducingtheoccurrenceofovergrownplants.However, customerdemandforspecificcoloror growthformcharacteristicsmaylimityour choices.Moresothanwithbedding plants,theresponseofherbaceousperennialstoPGRsdependsonthespeciesand cultivarselection.However,ingeneral, slowgrowingordwarfcultivarswillrequire lessPGRsthanmorevigorouscultivars. SomeplantspeciesorcultivarsareresponsivetospecificPGRs,butnotall

Environmentandculturalpracticescanbe manipulatedinthegreenhouseornursery toreduceplantgrowthandconsequently affecttheneedforchemicalgrowthregulation.Rootrestrictioncanbeusedtocontrolplantgrowthbyutilizingsmaller containersorbyincreasingthenumberof plantsperpot.However,thismethod workswellonlywhenotherproductionparameters,suchasamplelight,i.e.,wide spacing,andpropernutrition,areprovided.Plantsgrowninsmallpotsatclose spacingwillrequiremorechemicalgrowth regulationforadequategrowthcontrol thanthosereceivingamplelight. Reducingorwithholdingwaterorfertilizer isatraditionalmethodofcontrollingplant growth.Allowingplantstowiltslightlywill leadtoshorterplants,butexcessivestress ordroughtstressofsensitivecropsmay havetheundesirableeffectsofreduced plantqualityanddelayedflowering.Limitingtheamountofnitrogen,orusinghigh nitrateand/orlowphosphorousfertilizers, mayalsohelpcontrolplantheight,but tendstoproducethin,leggyperennials. Growerswhotendtoruntheirplants“dry” and/or“hungry”willneedlessPGRsto manageplantgrowth.NeverapplyPGRs toplantsthatarewiltedastheriskofphytotoxicityincreaseswithstress. Growingconditionsaffectplantheightand PGRneeds.Higherlightqualitytendsto limitplantelongation,thusresultingin shorterplants.Low-lightqualitycausedby inadequatespacingorcrowdingofthe croportoomanyhangingbasketsoverheadcanleadtoleggyplants.Lightquantityalsoaffectsplantgrowth.Higherlight

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A GUIDE TO GROWING TOP-QUALITY PERENNIALS | GROWERTALKS

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2012 PGR GUIDE levelsimproveplantgrowthandqualityas wellasbranching.Spacingwilloftendeterminetheneedfor,andamountof,additionalchemicalcontrolnecessaryfor optimumheightcontrol.Lowertemperaturescanbeusedtoreduceplantgrowth; this,however,mayalsoreducedevelopment,whichcandelayflowering.Soyou mayneedtoadjustyourcropschedulesto hityourmarketwindow.Lowerratesof PGRsarerequiredforplantsgrownunder lowertemperatures.However,ingeneral, higherratesofPGRswillbeneededfor plantsgrownoutdoorsundernurseryconditionsthanforthosegrowninthegreenhouse. Pinchingcanbeusedtoimprovethe shapeoftheplant,increasebranchingand controlexcessivestretch.However,the laborcostsofpinchingandthesubsequentdelayinplantdevelopmentmaynot makeitaneconomicallyfeasibleoptionof controllinggrowthofmanycrops.Thenew chemicalbranchingenhancers,Configure andAugeo,areeffectiveonawidevariety ofherbaceousperennialsinbothplug/liner andfinishedplantstages.Testmultipleapplicationstoimproveplantshapeand eliminatepinching. Optimizingplantgrowthcontrolrequires anunderstandingoftheeffectsofenvironmentalandculturalconditionsonplant growth.Experienceandon-sitetrialswill allowyoutocombinechemicalPGRswith anumberofnon-chemicalcontroloptions tomanipulateplantgrowthtoproduce highquality,compactplants.ThePGR ratetable(startingonpage8)containsresultsofuniversityPGRresearch,published reportsfromgrowers,chemicalcompaniesandplantsuppliers,aswellaslabel recommendationsforherbaceousperennials.Theseratesshouldbeusedasguidelinesforyourowntrials.Adjusttherates basedonyourlocation(higherratesinthe Sunbeltandlowerratesinnorthernareas), growingconditionsandculturalpractices, andthevigorofyourcroporcultivar.Keep recordsofyourresults,includingdetailson thestageofdevelopmentofthecrop,fer-

4 GROWERTALKS |

Note the linear height response of Rudbeckia Goldsturm at four weeks after foliar spray applications of 0, 15, 30, 45 or 60 ppm Sumagic (uniconazole).

tilizationandirrigationprograms,and weatherconditions. applyIng pgrs to herbaceous perennIals

Generally,growth-retardingPGRsshould beappliedjustpriortorapidshootgrowth. Formostspring-plantedperennials,thisis onetotwoweeksaftertransplantinga plugorliner,wheretherootsareestablishedandtheplanthasresumedactive growth.Onpinchedplants,applyPGRs afterthenewshootsarevisibleandstartingtoelongate.Foroverwinteredperennials,applythePGRshortlyafternew shootsemerge(2to4in.tall)orlaterals begintoelongate.Underwarmspring conditions,especiallyinacoveredcold frame,theseshootscanelongatevery rapidly.Thisiswheretheartofplant growthregulationismostimportant.You mustlearnhowyourcropgrowsand whentointervenetoobtainthedesiredresults.Remembertonotedetailsofcrop developmentinyourrecordsofPGRtreatments.Youmustgaugewhenrapidelongationwilllikelyoccurandtreattocounter it.Earlyinterventionmanagesplantgrowth andqualitybetterthanlateapplications. Linerdipsormediasprayscanbeveryeffectiveincontrollingearlygrowthofvigorouscultivars.Seelabelsforapplication guidelines.Testratessuggestedinthe tablestartingonpage8.Theseapplicationsareintendedtoprovideearlycontrol; andsubsequentsprayordrenchapplicationsmaybenecessary.

A GUIDE TO GROWING TOP-QUALITY PERENNIALS

Manygrowers,especiallynortherngrowers,prefertousemultipleapplicationsof growthretardantstobettercontrolplant growth.Asingleapplicationatahighrate earlyintheplantproductioncyclemaybe excessiveifgrowingconditionsarenotas goodasexpected.Anearlyapplicationat alowerrateprovidesmoreflexibility,but thetradeoffistheadditionallaborinvolved withmultipleapplications.Beawarethat excessiveratesofmanyofthesePGRs cancausepersistentgrowthreductionsin thecontaineroreveninthelandscape.It’s alwaysagoodideatoevaluatethelongtermeffectsofyourtreatmentsbygrowing someoutforyourselfortalkingwithyour customers.Becarefultoavoidlateapplications,especiallyofpaclobutrazoloruniconazole,astheymaydelayflower opening. check plants

HowwelldoesthePGRreallywork?The onlywaytoconfirmtheefficacyofaPGR istoleaveafewrepresentativeplantsuntreatedforcomparison.These“check plants”offeravaluableinsightintowaysto adjustfuturePGRapplications. Integratingchemicalgrowthregulatorsinto yourproductionpracticeswillhelpcontrol undesirableplantstretchandhelpensure awell-proportioned,highlymarketable crop.GT Joyce Latimer is a professor of horticulture at Virginia Tech, Blacksburg, Virginia.

2012 PGR GUIDE WideAssortmentofAvailablePGRs BYBRIANE.WHIPKER,NORTHCAROLINASTATEUNIVERSITY;ANDJOYCELATIMER,VIRGINIATECH

Here’s an overview of PGRs now available for use on ornamental crops

TAB LE

01.

The wide assortment of plant growth regulators available for ornamental crops.

c h e m I c a l

T

henumberofoptionsavailablefor controllingplantgrowthhasgreatly expandedoverthepastfewyears (Table1).Therearenowoptionsforcontrollinggrowth,expandinggrowthandencouragingbranching.Eachlabelhas specificrecommendeddoseranges,recommendationsandprecautions(Table2). BelowisanoverviewofthePGRsnow availableforuseonornamentalcrops.

Ancymidol

Citadel, Cycocel

Daminozide

Dazide, B-Nine

Dikegulac sodium

Augeo

Ethephon

Florel

Fluprimidol Paclobutrazol

(commercIal names: abIde and a-rest)—Ancymidolreadilymoves

chlormequat chlorIde (commercIal names: cItadel and cycocel)—Forornamentalcrops,it’s

mostcommonlyusedonpoinsettias,geraniums,osteospermumandhibiscus.Foliar chlormequatchlorideapplicationscanresultinaphytotoxicresponse(chlorosis), butthesymptomsareacceptablebecause they’reusuallycoveredupwithnewleaf growth.Incertaincrops(i.e.poinsettias, geraniumsandherbaceousperennials),a mixtureofdaminozideandchlormequat chloride(bothmaybeatreducedrates) maybeused.Thisusuallyprovidesfor

Abide, A-Rest

Chlormequat chloride

ancymIdol

throughtheplantandisusuallyusedon cropswhereotherchemicalsarenoteffective(mostnotablyinbulbcrops)oronvery high-valuecrops(i.e.plugs).Growersoften prefertheuseofancymidolonplugsbecauseofthelackofphytotoxicityandit’sa “safer”PGRtoapply(becauseitslimited residualallowstheplugstogrowoutofthe growthcontroleffectsafterbeingtransplanted).

p r o d u c t s

Uniconazole Benzyladenine (BA) Gibberellin (GA3 ) BA+GA 4+7 greaterheightcontrolandreducesthepotentialforphytotoxicity.Substratedrenches arealsoeffective,butnotcosteffective. damInozIde (commercIal names: dazIde and b-nIne)—Thismaterialisappliedonlyasa

foliarspraybecauseit’srapidlybroken downwhenappliedtothesubstrate.It’s highlymobileintheplantandwillrapidly movefromthepointofapplicationtoall partsoftheplant.Daminozideiseffective onmostcropsexceptlilies.It’shighlyeffectiveincontrollinggrowthofseedlingsin plugflatsandit’smosteffectiveincooler climates. dIkegulac sodIum (commercIal name: augeo)—Augeois

registeredforgreenhouseandnurseryuse.

Topflor Piccolo, Piccolo 10 XC, Bonzi, Paczol, Downsize (drenches only) Concise, Sumagic Configure Florgib, ProGibb T&O Fresco, Fascination Augeotemporarilystopsshootelongation, therebypromotinglateralbranching.It’s thusapinchingagentforornamentalcrops includingazaleas,bougainvillea,clerodendron,fuchsia,grapeivy,geranium,lantana, lipstickvine,verbenaandsomeofthe herbaceousperennials.Somephytotoxicity anddistortedgrowthcanoccurwith Augeo,sosufficienttimeisrequiredto allownewplantgrowthtocoveranydamagedleaves. ethephon phosphonIc acId (commercIal name: Florel)— Thismaterialisabsorbedbytheplanttissue,andduetoachangeinpHonceabsorbedintotheplantcells,releases ethylene.Florelisusedtopromoteflower budabortionandvegetativebranchingin crops.Florelisappliedasafoliarsprayat

A GUIDE TO GROWING TOP-QUALITY PERENNIALS | GROWERTALKS

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02.

TA BLE

COmPARiNG ATTRibUTes OF PlANT GROwTH ReGUlATORs

attrIbutes

plant growth regulator damInozIde + chlormequat chlorIde

ethephon

FlurprImIdol

dazIde, b-nIne

—

Florel

topFlor

85%

—

3.9%

0.38%

chemIcal

ancymIdol

chlormequat chlorIde

damInozIde

trade name(s)

abIde, a-rest

cItadel, cycocel

0.0264%

11.8%

active ingredient

paclobutrazol

pIccolo, pIccolo 10 Xc, bonzI, downsIze, paczol

unIconazole

concIse, sumagIc

0.4% 4% (PICCOLO 10XC)

0.055%

activity level

++

+

+

++

+

+++

+++

+++

multiple applications needed

++

+++

+++

++

++

+

+

+

Foliar spray

yes

yes

yes

yes

yes

yes

yes1

yes

Substrate drench

yes

yes

no

no

yes

yes

yes

yes

plugs/liners

plugs/liners

cuttings

-

plugs/liners

bulbs,

bulbs,

bulbs,

plugs/liners

plugs/liners

plugs/liners

application type1

Dips chemical absorption Ease of absorption Time (hours)

+++

+

+

+

++

+++

+++

+++

0.5-1.0

4

18-24

18-24

12-16

0.5-1.0

0.5-1.0

0.5-1.0

Factors that improve absorption Translocation within the plant

high humidity, limited air movement, cloudy days, early morning or late afternoon applications +++

+++

+++

+++

-

+

+

+

Leaves

+++

+++

+++

+++

+++

++

++

++

Stems

+

+

-

+

-

++

++

++

Roots

++

+

-

-

+

+++

+++

+++

15-50

1,000-3,000

1,250-5,000

Daminozide:

250-1,000

1-80

1-200

0.5-50

absorption sites

typical concentrations Foliar sprays (ppm or mg/L)

750-5,000 + Chlormequat 750-1,500

Drench (mg active

0.15-4.0

177-355

-

ingredient per pot)

(1.25 to 33.8 ppm)

(1,500 to 3,000 ppm]

-

++

-

+

-

+

+++

+

+

-2

0.01-2.0

0.01-8.0

0.01-1.0

(0.08 to 17 ppm)

(0.1 to 68 ppm)

(0.1 to 11 ppm)

-

++

++

++

++

+

+

+

other factors Does pink bark substrates affect drenches? Phytotoxicity potential

(Do not apply to stressed plants) Overdose potential

+

+

++

++

++

+++

+++

+++

Influence of water pH

-

-

-

-

pH 4.0 optimal

-

-

-