August 2003

Grower 101: Handling Unrooted Perennials By John Friel

Unrooted cuttings, from domestic or offshore suppliers, area standard product form for annuals and herbs. Now, perennial growers are usingthat same strategy.

Unrooted perennials are a hot topic, generating a lot ofbuzz at trade shows and seminars. Some growers are excited by the possibilitiesof a lower-priced format that slashes their input costs. Others see this newresource as a means to use more plants per pot, for a fuller look and fasterbulk-up. Still others want to add more hardy plant varieties to their offeringwithout losing valuable growing space to stock plants. Whichever scenario fits,growers must consider some very important factors before starting down therootless road.

Do Your Homework

Assess your infrastructure. Are your facility and staff equipped to handle unrooted perennialcuttings? If you’ve been relying on cell-pack liners or bare-root clumps tofinish pots, you probably haven’t had to invest in mist lines, a shade cloth orcoolers. You will need them to succeed with unrooted perennials.

Choose your supplier carefully. Select a supplier with a proven track record in perennials, a widevariety of offerings and a commitment to clean, healthy plants. Unit price isan important factor, but not the only consideration. Be sure to calculate thetrue “landed” cost to your door. Shipping, handling and customscharges vary widely between suppliers ? from less than $35 to almost $150per box, depending on your location and the origin of the cuttings. Ask aboutvolume and/or early order discounts.

Sweat the details.As with any unfamiliar procedure or product, if you are new to unrootedperennial cuttings, start slow. Order minimum quantities. Monitor resultscarefully until you gain confidence. Keep good records of mist schedules,chemical applications, rooting hormone rates and other inputs so you can refineyour processes for uniform results.

Beat the Clock

On receipt of cuttings.Check box count against the packing list. Report missing boxes to the carrieror your sales representative promptly. Open all boxes immediately and check thecount of cuttings against the packing list. Inspect cuttings for dehydration,heat or freeze damage, breakage or rot. Report any missing or damaged itemspromptly.

Most suppliers strictly limit the acceptable time forreporting problems and/or claiming credit. In most cases, this time is shorterthan allowed for claims and complaints on rooted plants. Never leave boxes insun, heat or below-freezing temperatures.

Stick cuttings ASAP.As soon as possible after you receive them, stick cuttings into apre-moistened, well-drained, soilless medium with a pH between 5.5 and 6.5.Stick cuttings just deep enough that they are anchored by the medium, normally1/4-1/2 inch deep.

If you cannot stick them immediately, unrooted cuttings canbe held for several days in a cooler at 35-45¡ F. Cuttings will deterioraterapidly in warmer temperatures and will suffer freeze damage if held colder.

Remember, unlike liners, unrooted perennial cuttings are notself-sufficient plants that can wait patiently, with occasional watering, untilyou’re good and ready to plant them. The clock started ticking when thecuttings were taken from the mother plant, thousands of miles from yourgreenhouse.

Rooting

Use appropriate rooting hormone. Most growers use IBA (potassium salt ofindole-3-butyric acid). Application rates vary according to species andvariety. Phlox subulata and Salvia greggii, for example, typically require noIBA, while Phlox paniculata and Salvia ‘May Night’ respond well to 1,000 ppm.There are two principal methods of application: 1) Apply as a light, uniformspray to cuttings within 24 hours after sticking. For best results, apply todry plants and wait until spray dries to resume mist. This can be done at theend of the day as mist is reduced. 2) Dip ends of cuttings into hormone priorto sticking.

Watch light and temperature levels. During high-temperature times of the year, shaderooting benches to approximately 50 percent light levels. Maintain greenhousetemperatures of 65-75¡ F. Provide good air circulation to forestall fungalgrowth. Cooler temperatures will inhibit root growth and set the stage forBotrytis. Warmer temperatures place undue stress on cuttings. Bottom heat (rootzone heating) is generally preferred over other methods.

Minimize wilting during rooting. High humidity levels must be maintained in yourrooting space to keep cuttings from dehydrating. This requires frequentmisting, not just watering.

Insect and Disease Control

Practice good sanitation. The high humidity level required to keep cuttings turgid while theyare rooting can also create ideal conditions for fungal and bacterial growth.Good cultural practices and a clean, well-ventilated growing space is your bestdefense against disease. Botrytis, the chief fungal threat, thrives in moist,stagnant environments. Provide good air circulation and adequate light. Foradditional disease protection, apply a broad-spectrum fungicide, such asHeritage, within 48 hours of sticking. Apply at the end of the day when mist isreduced. Rotate weekly with other fungicides, such as Chipco 26019, Cleary’s3336, Medallion or Pathguard.

Insects. Fungus gnatlarvae pose the biggest threat to good root development. If you see adultfungus gnats around your cuttings after sticking, their larvae are probably inyour medium, feeding on emerging roots. When necessary, drench with appropriatelarvicides such as Adept, Citation, Distance, Duraguard and Gnatrol.

Aphids can also occur during rooting. Useful pesticides includeAzatin, Botaniguard, Decathlon, Duraguard, M-Pede/Insecticidal Soap, MarathonII, Mesurol and Talstar GH.

Before using any pesticide, be sure it is registered for usein your state, and always follow label instructions.

Finishing

As plants develop root hairs, usually within 7-10 days,gradually increase the intervals between mistings. Most varieties are rootedwithin two weeks. Apply liquid fertilizer once or twice weekly, at 125 ppmtotal nitrogen.

When root systems are self-sufficient, your new plants areready to transfer into finished containers. Fertilizer and light levels shouldbe increased. A good all-around guideline for most perennials is a 20-10-20fertilizer at 300 ppm.