Increasingly, new annual varieties arereleased to growers as cuttings rather thanseed. This assures consistency in final prod-uct and increased production but requires adifferent set of skills from growers than what

is required with seed. From 1994 to 2005, the wholesale value of cut-

tings imported by U.S. greenhouse growersincreased 350 percent. In 2005, 495 million zonalgeraniums, poinsettias and New Guinea impatienssold in the United States had a wholesale value of$494 million. In this case, a single cutting represent-ed $.99 in potential revenue. Understanding theenvironmental requirements of unrooted cuttingsand how to handle them will help ensure success-ful rooting and a high-quality finished plant.

Part one of this series features cultural andenvironmental techniques that will ensure suc-cessful propagation. Next month’s article willfocus on how to prevent pathogens and diseaseand include information on light and tempera-ture requirements for creating an ideal propa-gation environment

Before They ArriveAs a grower, your attention and efforts are

most often, and appropriately, focused on theproduction cycle from the time cuttings arrive tothe finish week. It is easy to forget that importantcomponents of producing finished plants shouldoccur well before cuttings are stuck.

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Storage Temperature Guidelines*Storage Not Recommended Tropical (55-65° F) Temperate (35-50° F)

Bracteantha bracteata Angelonia angustifolia Achimenes hybridsCampanula species Antirrhinum majus Argyranthemum frutescensFuschsia hybrids Begonia x hiemalis Calibrachoa hybridsHelichrysum microphyllum, Clerodendrum paniculatum, Chrysanthemum x morifolium

H. petiolare and C. x speciosum, C. thomsoniae Dianthus caryophyllus and H. thianschanicum and C. ungandense D. carthusianorum

Heliotropium arborescens Crossandra infundibuliformis Diascia hybridsDahlia hybrids Hatiora gaertneri

Lantana camara and Euphorbia pulcherrima Nemesia hybridsL. montevidensis Evolvulus glomeratus Osteospermum ecklonis

Lobelia erinus Exacum affine Pelargonium species Portulaca oleracea Hibiscus rosa-sinensis and hybridsSutera cordata and Impatiens walleriana and Petunia x hybrida

Jamesbrittania hybrids I. hawkeri Plectranthus speciesIpomoea batatas Rhododendron hybridsLysimachia congestiflora Scaevola aemula

and L. nummularia Solidago speciesPentas lanceolata Verbena canadensis, Sanvitalia procumbens V. x hybrida, V. rigida,Schlumbergera truncate and V. tenera and V. tenuisecta

S. x buckleyiSolenostemon scutellarioidesTorenia fournieriTradescantia species

* From Cutting Propagation: A Guide to Propagation and Producing Floriculture Crops. 1st ed. Dole & Gibson.

Figure 1. In general, provide high relative humidity and the lowest temperature hardiness allows when storing cuttings. Shown hereare the storage temperature guidelines for tropical and temperate species.

Pictured are good examples of high-quality New Guinea impatiens cuttings. (Photos: Roland Leatherwood)

By RolandLeatherwood, Amy Enfield and Roberto Lopez

Researchers at North CarolinaState, Clemson and MichiganState Universities provideinsight on handling cuttingsfrom arrival to hardening inthe first of this 2-part series.

Getting The Most Out Of

Cuttings

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environment. The ideal environment will provideadequate moisture to maintain cutting turgor,minimize environmental stresses, provide highhumidity, prevent disease and promote rapidroot formation. Balancing these factors against theweather can be tricky. One must provide:

•Enough mist without saturating the soil. •As much light as possible without raising

temperatures. �

Prepare the propagation and handling areas bycleaning and disinfecting all the tools, surfaces andequipment. Check that the environmental controlsin the propagation area are working properly.Verify there will be enough clean flats andpathogen-free substrate on hand. Lastly, makesure there will be enough help available when thecuttings arrive to finish sticking within a day.

Arrival And StorageWhen your cuttings arrive, immediately

check the shipment for damage. Growers andshippers work hard to ensure the quality ofcuttings that arrive at your door, but occasion-ally, there are problems. Cuttings that are offcolor, watery, mushy, yellow or have a lot ofabscised leaves may be beyond saving. Whencontacting the supplier, be ready to describethe symptoms and have the order details athand. If you decide to stick poor or damagedcuttings, keep in mind the possibility of losingcuttings during propagation, which may ulti-mately cost more than waiting for a replace-ment shipment. Sometimes it is worth waitingfor new cuttings to arrive. Regardless of condi-tion, make sure the supplier batch sticks staywith the cuttings. Doing so will help resolveany problems that may arise later.

Even the best-quality cuttings will degradequickly if not handled properly after arrival. It isbest to stick cuttings immediately, because thebetter the cutting condition when stuck, thequicker they root and are ready to be transplant-ed. Realistically, this is not always possible. Forthe vast majority of species, holding cuttings intheir packaging for a few hours in a cool, darkplace is almost never a problem.

For longer-term storage, it is important toremove the cuttings from their packaging andlayer them in damp papers. Make sure they arenot wet, since wet cuttings are very susceptibleto Botrytis and bacterial rot during storage.Tropical and chill-sensitive species can bestored at 55-65° F, while temperate species canbe stored at 35-50° F (see Figure 1, left). In gen-eral, provide high relative humidity (80-95 per-cent) and the lowest temperature hardiness

allows. For some species, storage is not recom-mended under any circumstances.

Rooting ConsiderationsRooting compounds, such as IBA, mimic plant

hormones, improve rooting uniformity and pro-mote greater root mass. They are sometimes appliedafter cutting harvest and before shipping but fre-quently must be applied by the grower. Rootingcompounds can be applied as a powder, dilutesoaking solution or concentrated quick dip. Thequick-dip method allows bundles of cuttings to betreated together, thereby shortening the treatmenttime (see Figure 2, below). Commonly used concen-trations are in the 1,000- to 3,000-ppm range. It isimportant that the concentrated hormone dip onlycomes into contact with the stem and not the grow-ing tip, as it can cause twisted and distorted growth.

Rooting media is a critical component of prop-agating unrooted cuttings and has several impor-tant functions. The substrate should hold the cut-ting in place, provide moisture to the cuttingwhile being well drained and provide airexchange around the base of the cutting. Rootingmedia is composed of organic and mineral com-ponents, usually peat and perlite, vermiculite,pumice, polystyrene or rockwool. The key is aera-tion. Soggy media will rot cuttings, and waterfilms on cutting bases can hinder rooting.

For some crops, foliar fertilization through amist system is useful. Some growers choose tofertilize with every other watering. Others elect toprovide constant liquid feed at 50-ppm nitrogenthrough the mist system throughout propagation.Though convenient, constant liquid feed via mistcan lead to excessive algae growth on walkwaysand benches. It may be easier with small batchesof cuttings to apply fertilizer with a sprayer in theevening after the mist is off for the night. Whendirect sticking cuttings, it is often useful to incor-porate slow-release fertilizer into the rootingmedia. The slow release will not promote root ini-tiation but will boost root development.

The Ideal EnvironmentMany growers find changing weather conditions

create a challenge in managing the propagation

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Preparing an IBAIBA (per liter of solution) NAA (per liter of solution) Stock concentrate and dilution

Hormone 50% Final Final Concentration ppm mg g ppm mg g concentrate Ethanol Solution

250 IBA : 125 NAA 250 250 0.25 125 125 0.125 25 ml 975 ml 1,000 ml

500 IBA : 250 NAA 500 500 0.5 250 250 0.25 50 ml 950 ml 1,000 ml

1,000 IBA : 500 NAA 1,000 1,000 1 500 500 0.5 100 ml 900 ml 1,000 ml

5,000 IBA : 2,500 NAA 5,000 5,000 5 2,500 2,500 2.5 500 ml 500 ml 1,000 ml

10,000 IBA : 5,000 NAA 10,000 10,000 10 5,000 5,000 5 1,000 ml 0 ml 1,000 ml

The hormone concentrate (HC) is the stock solution (1% IBA + 10,000 ppm : 0.5% NAA + 5,000 ppm). To make 1 liter (1,000 ml) solution of 250 ppm IBA : 125 ppm NAA, usethe formula:Concentrate HC X Volume HC = Concentrate solution X Volume solution10,000 ppm IBA (HC concentrate) X Vol. = 250 ppm X 1,000 ml;25 ml of HC concentrate stock solution + 975 ml 50% ethanol = 250 ppm IBA : 125 ppm NAA in one liter.

Figure 2. Varying concentrations from 250 to 10,000 ppm of IBA and NAA are used in commercial plant propagation depending on species. To have the correct concentration on hand, the hormones are soldas concentrates to be diluted when needed by the grower. Shown are volumes of commercial hormone concentrate to be blended with a 50-percent-ethanol solution. The resulting concentrations of IAA andNAA are given in ppm, mg and grams. Use an EPA-approved end-use formulation (e.g., Dip ‘N Grow [1% IBA + 0.5% NAA]). Duration of basal dip should last 3 to 5 seconds.

Top: These boxes contain newly arrived cuttings ready forsticking. Bottom: These New Guinea impatiens cuttings weredamaged during transport.

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•Media and air temperatures that encour-age rooting but are not high enough to stressthe cuttings.

•Limited air movement.There must be adequate moisture, light and air

movement control so the cuttings are optimizedduring cool, rainy days as well as sunny, hotones. In the ideal environment, most unrootedcuttings will root in 2-3 weeks.

Moisture MaintenanceThere are many methods for providing mois-

ture to unrooted cuttings during propagation.The idea is to provide cuttings with enoughmoisture to minimize wilt and keep humidity ashigh as possible, thereby reducing transpira-tional water loss. However, a slight degree ofstress is useful in encouraging root initiationand development.

You never want to see wilted cuttings, butthey should be kept right on the edge of it.This is most often achieved by providing aluxuriant amount of moisture during the firstfew days after stick, then reducing the fre-quency of application during subsequent days,particularly after callus formation. Thisapproach has the advantage of not only allevi-ating the moisture stress encountered duringshipping but also avoiding the soggy mediaproblem and Botrytis rot.

The most common watering system used inpropagating unrooted cuttings is intermittentmist. Mist lowers leaf temperatures throughevaporative cooling, which reduces transpira-tion. Fungal spores of some pathogenicspecies are unable to germinate on wet leaves,so fungal diseases are reduced, but strictattention to cleanliness is required. Foliar

application of mineral nutrients is also possi-ble through mist systems. However, mist sys-tems can quickly saturate the media, so theymust be monitored carefully and adjustedwhen too much water is applied.

Fog systems are similar to mist systems butproduce a much smaller water particle underhigher pressures. These systems maintain highrelative humidity with less chance of saturatingmedia and can be used for evaporative coolingof cuttings. Fog and mist systems are suscepti-ble to clogged nozzles due to poor water quali-ty, so provide adequate filtration.

Poor water quality can damage cuttings.Electrical conductivity, pH and hardness should

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Write in 720 Write in 744

Hanging mist lines are a common method of irrigation inpropagation.

Irrigation (Mist) Water Guidelines*

Maximum Tolerable

Category Reading

Electrical Conductivity (EC) 0.75 mS/cm

pH 5.5 – 7

Alkalinity 1.5 me/L (75 ppm CaCO

3

equivalent)

Hardness 3.0 me/L (150 ppm CaCO

3

equivalent)

Calcium & Magnesium 3-5 ppm per 1 ppm magnesium

Specific Elements

Sodium 50 ppm

Chloride 70 ppm

Chlorine 2 ppm

Iron 4 ppm

Manganese 0.5 ppm

Zinc 0.3 ppm

Copper 0.2 ppm

Borate 0.5 ppm

Fluoride 0.5 ppm

Lithium 0.5 ppm

*Also see North Carolina Cooperative ExtensionService Horticulture Information Leaflet 557: WaterConsiderations for Container Production of Plants.Baily D., Bilderback T., & Bir D. www.ces.ncsu.edu/depts/hort/hil/pdf/hil-557.pdf

Figure 3. Water quality can have an enormous impact oncuttings. Shown here are recommended guidelines for irrigationwater quality.

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all be checked before installingeither system. High concentrationsof dissolved minerals such as ironcan precipitate onto surfaces indedicated propagation areas.Bacteria in mist water can cause anoutbreak of disease. Suggestedmaximum tolerable values of themost important factors are listed inFigure 3, left.

The System WorksFog and mist systems are

unique among methods of provid-ing moisture because they canlower temperatures during highheat situations. While it was men-tioned previously that air move-ment should be limited duringpropagation, air movement issometimes essential to balancelight, heat and moisture underhigh heat conditions.

This is how the system works:The fog or mist system is operatedcontinually or as frequently aspossible without saturating themedia. The air temperature ismonitored. When it reaches a pre-set maximum, the vent fans areturned on, and moisture is evacu-ated from the greenhouse. Theresulting evaporation can dropcutting temperatures as much as10-15° F. This is a tricky way todrop temperatures, so monitorcarefully. Check with other grow-ers who have used it before tryingit on a whole crop.

Other methods of providingmoisture are far simpler than mistor fog systems. Non-misted enclo-sures of white plastic tents can beerected over the cuttings on thebench. Once or twice a day the inte-rior is misted to keep the humidityhigh. This works well for speciesthat do not tolerate excessive mois-ture but require careful monitoringfor disease and excessively hightemperatures.

Perhaps the simplest method ofmaintaining moisture around cut-tings is contact systems. Usuallycuttings are stuck and thenwatered in. A non-woven fabric islaid over top and periodicallydampened as necessary. Contactsystems have the advantage of notrequiring dedicated space forpropagation, and the cuttings, ifdirect stuck, can be grown on inplace. Monitoring cuttings anddiseases can be a problem withcontact systems.

W. Roland Leatherwood is a Ph.D.student in the Department of

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Horticulture Science at NorthCarolina State University. He canbe reached at roland_leatherwood@ncsu.edu. Roberto Lopez isa Ph.D. student in the Departmentof Horticulture at Michigan StateUniversity. He can be reached atlopezro4@msu.edu. Amy Enfield is

research at North Carolina StateUniversity, Clemson University andMichigan State University.

a Ph.D. student in the Departmentof Horticulture at ClemsonUniversity. She can be reached ataenfiel@clemson.edu.

Author’s note: The authors wish tothank cutting suppliers, greenhousesand suppliers that support cutting

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LearnMoreFor more information related to this article, go to www.gpnmag.com/lm.cfm/gp110604

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