Pot Plant Production

An extra layer of plastic film reduces heat loss but also reduces light levels in a lily production greenhouse (top). Double cropping with baskets has a similar effect (bottom).

The Easter lily crop for 2010 follows a mid-date crop schedule. A mid-date schedule for Easter that falls between April 3-15 is best from a grower perspective because it doesn’t require any special management tactics to either slow down or speed up crop development. Also, in northern climates, having the crop out of the greenhouses at the end of March allows plenty of time to fill them up for spring production.

A trend that has occurred the last few years is an attempt by Easter lilies growers to conserve energy and reduce their production costs. Some growers have added an extra layer of plastic film, suspended above the trusses, to provide additional insulation. Other growers have double cropped their lilies with overhead baskets.

With energy prices on the rise again, growers will face the same pressures in 2010. Their efforts to lower costs can impact plant quality. As overhead shading increases, growers will need to rely on growth regulators to control stretching and leaf yellowing associated with reduced light levels.

Critical dates
For Easter 2010, start case-cooling bulbs by Oct. 25 (23 weeks before Easter). If bulbs arrive later than this date and you can’t provide six weeks of bulb cooling by Dec. 6 (17 weeks before Easter), start the greenhouse forcing anyway and just substitute one week of insurance lighting for each week of cooling still needed.

For pot-cooled bulbs start six weeks of bulb cooling by Nov. 15 (20 weeks before Easter) and start greenhouse forcing 14 weeks before Easter. Ideally pot-cooled bulbs should be potted by Oct. 25 and held at 60oF-62oF for three weeks prior to the Nov. 15 cooling date in order to stimulate root development. If you don’t have time for the full three weeks rooting period, give them as much as is available until the Nov. 15 start date for cooling.

Regardless of the bulb cooling method used, lilies should reach the visible bud stage around Feb. 21 or six weeks before Easter. Lilies at this stage will reach full bloom in time for shipping one week before Easter.

Lilies are a challenging crop even in seasons when the schedule permits adequate time for proper forcing. Bulb response can be notoriously variable from year-to-year and even from batch-to-batch due to variations in summer field conditions during bulb production and handling after the bulbs are harvested.

Easter 2010 outlook
Easter falls on a mid-date in 2010 (April 4). This is on the early end of the mid-date calendar but will allow enough time for proper programming and forcing. Average heights and times for forcing are presented in this schedule. Adjust the schedule according to plant growth, bud development, starting time and past experience.

Pot-cooled bulbs
Pot-cooled bulbs are normally potted and held for three weeks at 63°F before six weeks of bulb cooling (at 40°F-45°F) begins. The bulbs then require 14 weeks of greenhouse forcing. This entire process requires 23 weeks from initial potting to Easter. This is the same process that is used for naturally cooled or controlled-temperature-forcing bulbs.

Case-cooled bulbs
Case-cooled bulbs require six weeks of cooling followed by 17 weeks of greenhouse forcing to flower in time for Easter. Be sure that commercially case-cooled bulbs arrive and are planted by Dec. 6.

If you cool your own bulbs, start Oct. 25 (23 weeks before Easter). Insurance lighting should not be needed this year but can be used if you can’t complete the full six weeks of bulb cooling.

Insurance lighting
Provide insurance lighting if you know or suspect that the bulbs have not received the entire six weeks of cooling by the time greenhouse forcing is scheduled to begin. Insurance lighting refers to night break lighting used to produce a long day photoperiod. When insurance lighting is used immediately following shoot emergence it produces the same effect as bulb cooling or vernalization. Insurance lighting can be used to substitute for inadequate bulb cooling. Provide one day of insurance lighting for each day of lost cooling. Incandescent, fluorescent or high intensity discharge lighting in excess of 10 footcandles from 10 p.m. to 2 a.m. daily will provide the necessary night break.

Fertilization
Start feeding with a soluble fertilizer formulation when lilies emerge and continue feeding to within seven days of sale. Combine calcium nitrate (three parts) with potassium nitrate (two parts) to make a 15-0-18 soluble fertilize, or use a commercial 15-0-15 formulation.

If phosphorus was not added to the growing medium, 20-10-20 can be used on an alternating basis with a 15-0-15. Fertilizer rates should range from 200-400 parts per million.

Do not allow the growing medium electrical conductivity to exceed 3-3.5 mmhos per centimeter based on a saturated media extract analysis. Stop fertilizing just before sale.

Provide one clear watering before lilies are shipped to reduce salt levels in the medium and to maximize lily keeping quality. Do not withhold water or fertilizer to slow development. Do not over water or root rot problems may occur.

Reduced light levels increase reliance on growth regulators to control stretching and leaf yellowing.

Workers preparing lilies for shipping by stripping lower leaves that yellowed prematurely.

Leaf yellowing and flower senescence
To prevent early-season (seven to 10 days before visible bud) and mid-season (seven to 10 days after visible bud) leaf yellowing, spray Fascination at 10/10 ppm. Fascination contains two active ingredients and recommendations include the concentration of each. Only apply Fascination to lower leaves and cover thoroughly.

To prevent late-season leaf yellowing and post-harvest flower senescence, spray 100/100 ppm Fascination to thoroughly cover all foliage and flower buds. Make the application when buds are 3-3½ inches long and not more than 14 days before shipping or cooling. Fascination protects leaves from yellowing for up to 14 days.

Side effects of Fascination include stem stretch. Avoid direct contact of the spray to immature leaves during early- and mid-season applications.

Disease and pest control
Before planting, clean bulbs of debris removing any damaged scales, especially scales that show evidence of infection. Once potted, root rots associated with Rhizoctonia, Fusarium and Pythium are a concern. Drench immediately with Banrot or Insignia, broad-spectrum fungicides, or treat to control these diseases separately by selecting from the fungicides specifically registered for Rhizoctonia, Fusarium and Pythium control on lily.

Materials registered for Rhizoctonia and/or Fusarium include 26GT, 26/36, Contrast (Rhizoctonia), Sextant, and Terraclor WP (Rhizoctonia). Materials registered for controlling Pythium include Alude, Banol, Subdue Maxx, and Truban. Check with manufacturers regarding compatibility when tank mixing fungicides for Pythium with Rhizoctonia/Fusarium controlling materials. Fungicides may need to be re-applied later in the crop, check labels for guidance.

Aphids, fungus gnats and bulb mites are a major concern. Use only smokes or aerosols once plants are in bud.
Numerous chemicals are available for aphid control, including, Safari, Celero, Flagship, Tristar, Marathon, DuraGuard, Distance, Enstar II, Preclude TR, Tame, Ultrafine Oil, Insecticidal Soap, Talstar and Endeavor. Fungus gnats can be controlled with many of these same chemicals as well as Citation, Adept, insect parasitic nematodes (Nemasys, NemaShield, Scanmask) and Gnatrol.

Bulb mites (Rhizoglyphus robini) represent one of the more troublesome insect pests on lilies. Duraguard is labeled as a drench for soil borne organisms that may include bulb mites. Bulb mites are more likely to attack physically damaged bulbs so be sure to control fungus gnats and handle bulbs gently.

Registration of pesticides varies by state so consult and follow labels for registered uses. To avoid any potential phytotoxicity or residue problems, spot test a few plants first before widespread application. No discrimination is intended for any products not listed.

The first growth regulator application for height control should be made when lilies reach a height of about 3 inches, typically 11-12 weeks before Easter.Controlling height
Apply A-Rest, Chlormequat E-Pro, Concise, Cycocel, Topflor or Sumagic as needed when shoots are 3-5 inches tall. Split applications provide the best results. Any of these growth regulators can be applied at one-fourth to one-half the normal rate, as needed, to control height.

Reduce the concentration of Sumagic applied when combined with DIF (difference between night and day temperature). Use DIF, or a cool morning DIP, to control lily height. Equal day/night temperatures, high night/low day temperatures or cool morning temperatures will keep lilies short.

Lily storage
Lilies can be stored for up to 10 days in the dark at 35°F-45°F when buds turn white but before they open. Treat for Botrytis prior to moving lilies to cold storage. Materials registered for Botrytis control include 26GT, 26/36, Daconil, Exotherm Termil, Sextant and Protect DF. Follow label directions.
Water lilies thoroughly before starting cold storage. After removing from the cooler, place lilies in a shady location to avoid excessive wilting.

Graphical tracking
Monitor lily height regularly during forcing. If height exceeds the target size, run a negative DIF to slow stem elongation. If height is less than the target size, run a positive DIF to increase stem elongation.

All agrichemical/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations. If the information does not agree with current labeling, follow the label instructions. Where trade names are used for identification, no product endorsement is implied nor is discrimination intended.