Easter Lily Forcing Schedule

Below was the recommended schedule for Easter Lily Production for Easter 2008 (March 23, 2008.)

Soil Requirements
* Use a good commercial artificial growing mix that is a light coarse airy mix. The soil should contain no super phosphate with a pH between 5.8 and 6.5 containing good levels of calcium and some available nitrate nitrogen fertilizer.

Planting Depth
* Plant into a standard depth pot with 1 inch of media below the bulb, assuming bulb and peat moss temperatures were satisfactory during cooling.

Temperature Requirements
* Start crop between 60 and 62 degrees at night and between 65 and 68 degrees during the day.

Easter 2008 Schedule Courtesy of Richard McAvoy, Professor & Extension Specialist – Greenhouse Crops - University of Connecticut

Weeks		Forcing Method
Prior to Easter	Date	Case-Cooled	Pot-Cooled (CTF)
23	Oct. 14	Bulbs dug, shipped & in hand by mid-Oct.   Start bulb programming as soon as bulbs arrive but no later than 23 weeks before Easter . Consult article for recommendations if bulbs arrive late.
		Cool at 40-45F for 6 weeks	Pot & allow roots to grow at 60-62F for up to 3 weeks
20	Nov. 4	---	Cool at 40-45F for 6 weeks
17	Nov. 25	Pot no later than 17 weeks before Easter Force in greenhouse at 60-62F in pot.	---
14	Dec. 16	Roots visible by week 15 & shoots emerge by week 14. Start fertilizing & keep moist.	Force in greenhouse (at 60-62F) no later than 14 weeks before Easter.
		Begin insurance lighting (10pm to 2am) as soon as shoots emerge. Provide up to 2-weeks of insurance lighting as needed to reach a total of 1000-hours cooling plus lighting.
13	Dec. 23	1-2" tall. Keep lilies moist & use fungicide drench as needed.
12	Dec. 30	2-3" tall.   Bud initiation coincides with stem root development. Run 60-62F-day/ nights until bud set is complete.
11	Jan. 6	3-4" tall.    Apply growth regulator when 3-5” tall.   Bud initiation nearly complete, maintain temperature below 65F until done.
10	Jan. 13	Check for bud set.   Begin leaf counting   & graphical tracking. Keep greenhouse cool if ahead of schedule.
9	Jan. 20	5-6" tall. Adjust temperatures as needed.   Space lilies to avoid yellow leaves & stretching. Apply Fascination to lower leaves (7 to 10 days before visible bud) if leaf yellowing is evident.
8	Jan. 27	Check for aphids & root problems.   Apply Marathon sometime during weeks 10, 9, or 8. Soil test & if leaf scorch is evident, use calcium nitrate for balance of schedule.
7	Feb. 3	7-8" tall.   Lilies are about half final height.   42 days to sale.   Buds can be felt. If buds are visible on early planting run 60F until finish.
6	Feb. 10	35 days to sale. Buds should be visible no later than 30 days prior to sale. Grade for uniformity as buds become visible.
5	Feb. 17	Buds 1/2-1" long. Re-apply Fascination if necessary.
4	Feb. 24	Buds   1-1 1/2", some bending down.
3	March 2	Buds 1 1/2-2” long.   If aphids present, use a total release smoke or aerosol.
2	March 9	Buds 2 1/2-4" long, some turning whitish. Stop fertilizing just before sale & apply clear water once. Cool lilies at 35-45F to hold. Prior to cold storage, Fascination can be applied to entire plant.
1	March 16	Ready to sell.   Shade lilies once removed from storage.   If needed, use EthylBloc prior to shipping.
0	March 23	Easter 2008

Overall Greenhouse Growing Information

Easter 2008 will be a rare event. It is the earliest Easter date any grower alive today will ever have to meet. In 2008 Easter falls on March 23. The last time Easter came that early in the season was 1913. In fact over the next 100 years (from now until 2108) Easter only fall as early as March 25th three times -- two days later than this year. On average Easter dates as early as March 26 only occur once every 15 years. Early Easters present a couple of problems. First, a normal schedule requires a full 23 weeks to complete. That means growers will need bulbs in-hand by October 14, 2007 to run a normal forcing program and bring the crop in for the March 23 Easter sales season. This is unlikely to happen as bulbs typically are not available until late October at best, and that means that growers will have to cut corners at certain points in the schedule to hit the early 2008 date. The second problem with an early date, especially in northern climes, is the difficulty in pushing high temperatures late in the schedule while we are still in winter weather. Let’s look at what you can do the make your crop in 2008.

The 23-week schedule: With both pot-cooled and case-cooled bulbs the full cropping schedule requires 23 weeks. This schedule brings the crop in one-week prior to Easter Sunday. Both cooling methods, call for six-weeks of bulb cooling or vernalization, 3 weeks of root & shoot development prior to emergence, and 14-weeks forcing in the greenhouse. If we are going to cheat, we need to identify the critical steps and make the best possible choices in cutting corners. Let’s look at the pot-cooled crop first.

Pot-cooled bulbs (this includes naturally-cooled bulbs) are potted as soon as bulbs arrive, preferably by week 23 on the schedule (Oct 14 this year) and then held at 60-62F for 3 weeks. The potted bulbs are then cooled for six weeks (40-45F) or until week 14, at which time they are moved to the greenhouse for forcing. During the initial three weeks (starting on week 23) roots develop and the shoot meristem matures. These physiological developments improve cold perception during vernalization and help to produce more uniform shoot development. However, this is the first place to cheat if time does not allow the full schedule. You can cut the three weeks down to one. This will allow a little time for some root development to begin before cooling.

The 6-weeks of bulb cooling is the next key step. We recommend 1000-hours or 6-weeks of cooling as a general rule but lilies will spout and bloom on a reasonable schedule with as little as 4-weeks of cooling. Also, we have an ace card to play here in that we can use up to two weeks insurance lighting when the shoots first emerge to make up for any shortage in cooling hours (up to 2-weeks). The final production phase is the greenhouse forcing, for pot-cooled bulbs this means 14-weeks in the greenhouse beginning December 16, 2007 for this years schedule. Growers should be very hesitant to short the greenhouse-forcing portion of the schedule especially this year, and especially if they normally have to push hard to finish since it may be very hard to force bud development with high temperatures in late February and early March. Therefore, the second place to cheat, if needed, would be on the bulb-cooling portion of the schedule. Make sure you expose the potted bulbs to at least 4-weeks of cooling at 40-45F (5-weeks is even better if time permits), then use insurance lighting for up to two weeks, to make up the difference in lost cooling (more on insurance lighting later).

Now let’s look at the case-cooled crop. Again, the full schedule calls for 23 weeks from start to finish. Typically case-cooled bulbs are placed in the 40-45F cooler starting on week-23 or October 14 this year. After 6-weeks, bulbs are potted and moved to the forcing greenhouse (at 60-62F) beginning 17-weeks prior to Easter or Nov. 25, 2007. Shoots take longer to emerge with case-cooled bulbs, but should be up by week 14 (Dec. 16). The greenhouse-forcing phase of the schedule is the same as with the pot-cooled crop. With case-cooled bulbs the critical dates are the onset of bulb vernalization (cooling at 40-45F) and the start of greenhouse forcing. If you cool your own bulbs, you’ll know how late you got started. For example, the 2008 schedule calls for an Oct 14 start date but if you do not receive your bulbs until Oct 28, then you are already two weeks behind. Here’s what I recommend if you are two or more weeks behind at the onset. Cool-bulbs for at least 4 weeks then pot and begin forcing. As shoots emerge, immediately begin insurance lighting for up to two weeks. If you are still behind, you will have to make up for lost time later in the crop (after bud initiation).

If you buy in case-cooled bulbs, it will be important to know exactly how much cooling they received. You want the bulbs on hand so that you can pot and beginning forcing by week 17 (November 25). If you know or suspect that the 6-weeks of cooling was incomplete, use insurance lighting. If the bulbs arrive after November 25, you will have to make up time during greenhouse forcing but after bud initiation.

Insurance Lighting:

Insurance lighting refers to night break lighting used to produce a long day photoperiod. When applied immediately after shoot emergence, the long day photoperiod has the same affect as bulb cooling. It reduces the time to flower as well as the number of leaves and flowers produced. [The reduced flower number is a negative consequence that we accept in order to make the plants flower in a reasonable time frame.] Therefore, insurance lighting can be used to substitute for inadequate bulb cooling. Provide one week of insurance lighting for each week of lost cooling - up to a total of two weeks. For example, if your bulbs arrive too late to begin case-cooling on week 23, or if weather conditions prevent you from achieving 1000 hours of natural pot-cooling by week 14 (December 16), you can still start greenhouse forcing on time by providing a week of insurance lighting for each week of lost cooling time. Incandescent, fluorescent, or HID lighting in excess of 10 foot-candles from 10 pm to 2 am daily will provide the necessary night break. It is important that the shoots perceive the long day photoperiod (the insurance lighting) as soon as they emerge. And since lilies do not emerge all at once, growers should gather groups of lilies as they emerge and begin the insurance lighting. Gather pots with emerging shoots 2-3 times per week and make note to how long each block receives the insurance lighting. This is preferred since insurance lighting will also cause stretching, therefore excessive lighting, more than two weeks, provides no additional benefit in terms of vernalization and will only serve to produce tall lilies. Note that the insurance lighting period will coincide with lily bud initiation so keep temperatures between 60-65F day and night, during this period.

Greenhouse forcing:

With both pot-cooled and case-cooled lilies, greenhouse forcing starts at the end of the bulb-cooling period. Typically this is 17-weeks before Easter for case-cooled bulbs and 14-weeks before Easter for pot-cooled bulbs. The difference in the two schedules just reflects the stage of shoot development. With pot-cooled bulbs the shoots are either at the soil surface or already emerged as soon as forcing begins (week 14). In contrast case-cooled bulbs, will take up to three weeks to emerge. So either way, the shoots on both crops should be emerging by about week 14 (December 16).

Bud initiation begins soon after lilies emerge, and should be completed no later that mid-January this year, when shoots are 3"-5" tall. The development of stem roots coincides with flower bud initiation. During this period, temperatures of 60-65F day and night desirable (63F is ideal), but it is imperative that temperatures do not exceed 65F until bud initiation is complete. This is important, don’t try to catch up with high temperatures at this point in the schedule. If you find yourself short on forcing time in the greenhouse, wait until bud set is complete before attempting to speed up plant development with higher temperatures.

Leaf counting & forcing temperatures : Begin using the leaf counting technique to track lily development as soon as bud initiation is complete. You should be able to start this by week 10 or January 13. This will allow you plenty of time to determine if lily development is on track and to make the necessary adjustments. Don’t wait to start leaf counting this year. Too often growers do not realize their lilies are behind schedule until after visible buds fail to appear with about six weeks to go. With an early Easter, winter weather may limit your ability to make up a lot of lost time at this point in the crop.

Run lower average daily temperatures (55-60F) if lilies are ahead of schedule – an unlikely circumstance this season, or higher temperatures (70F) if behind schedule. Begin to assess crop development early so that temperature extremes can be avoided later. Typical leaf unfolding rates vary from approximately one leaf/day at 53F to 1.5 leaves/day at 63F, 2 leaves/day at 72F and 2.5 leaves/day at 82F. Forcing temperatures between 55-70F produce the highest quality lilies and are most fuel-efficient.

Once lilies reach visible bud they will typically flower in 30 days at 70F and 35 days at 65F. Monitor bud development by measuring bud length. Adjust temperature as needed to stay on schedule. A ‘bud stick’ is a useful tool to gauge the rate of lily bud development and the time needed to finish at a specific temperature. If you don’t have a bud stick, refer to Table 1 to estimate rate of bud development. I recommend you assess bud development early and adjust temperatures at that time. In late Easters growers in northern climates often hold off on forcing bud development until the last two weeks, knowing that high natural light and warm weather in early- to mid-April will assist in this effort. But this season, you will have to push in late February and early March for the March 16 sales date. Ask yourself, what conditions can I expect this time of year? If winter weather patterns are still likely at your site, start your push earlier.

Uneven temperatures produce uneven crops. Use horizontal airflow to equalize greenhouse air temperatures. If you need to use temperatures above 80F to push lilies at the end, take care to maintain adequate soil moisture and humidity levels or lily development may stall and buds may abort.

Table 1 . To use this table, measure the length of your lily buds. Move across the table horizontally to the column that lists the temperature you are running in your greenhouse. The number you see is the approximate number of days that it will take to the buds to open at that temperature.

Length of lily buds (inches)	Greenhouse air temperature (24-hour average)
	59F	64F	70F	75F	81F
	Approximate number of days to flowering at each temperature
2”	24	20	17	15	12.5
3”	15	13	11	9.5	8
4”	9.5	8	7	6	5
5”	5	4.5	3.5	3	2.5

Height control

Growth regulators should not be applied until after flower buds have set (early- to mid-January 2008). Use DIF to control lily height during flower initiation. Equal day/night temperatures or cool morning temperatures will produce a DIF effect and keep lilies short. The conventional PGR program uses a single application of A-Rest, Concise, Topflor or Sumagic as needed when shoots are 3-5" tall. The dose used is high enough to provide control through to about week 6. However, in practice many growers are much more creative and a typical program may call for weekly applications as needed to either slow stem stretch with a growth retardant such as Sumagic, or increase stretch with gibberellins such as in Fascination, or to prevent leaf yellowing in closely spaced plants (also with Fascination). Growers that use this program are applying growth retardants to lilies that are well past the visible bud stage.

Even if you are incline to be more conservative in your PGR practices, split applications are preferred. Split applications produce the most desirable plants. With split applications, use half the normal dose at the first application and then a one-quarter to one-half dosage in subsequent applications (depending on the number of applications you plan to use and the amount of control needed). Lilies exposed to high concentrations of growth retardants have a greater tendency to develop lower leaf yellowing in the later stages of production. Some growers have been applying low concentrations of Sumagic just as the shoot emerges and then following with a second application when the bud initiation period is over. I prefer to allow bud initiation to be completed before altering natural hormone levels in the plant. Plus if you are maintaining 63F day and night, as you should, you already have a zero DIF regime that will limit stretching during this phase. If you still wish to apply PGRs at this time, I recommend the lowest effective dose (1/8th –1/4th the normal dose). Just apply enough to hold the plant for 7-10 days rather than the typical 3-5 weeks.

Nutrition

Proper nutrition is also important in early crop development. Inadequate nitrogen early in development leads to small bottom leaves and small leaves limit the potential for subsequent growth. To get plants off to a good start, provide a single application of 400-600 ppm nitrogen at first irrigation, when lilies begin to emerge after programming. This will help to stimulate early leaf development. Remember the more leaf area a plant has, the more sunlight the leaves will gather and that translates into greater growth. Phosphorus is also important in early lily development. We often limit phosphorus in lily nutrition to avoid leaf scorch caused by fluoride toxicity. (Fluoride is a found in phosphorus based fertilizers and some soil amendments). But phosphorus is also important for strong root development. Use a complete fertilizer formulation, such as a 20-10-20, for the initial feed.

After the initial feeding use a 15-0-15 formulation, but if phosphorus was not added to the medium use the 20-10-20 formulation on an alternating basis with the 15-0-15. Fertilizer rates should range from 200-400 ppm. Do not allow medium EC to exceed 3-3.5 mmho/cm based on a Saturated Media Extract. Periodic nutrient testing is advisable during the crop. Testing the nutrient status of young but fully expanded leaves will provide the most accurate picture of lily nutritional health. Leaf tissue nutrient content should fall in the following ranges, 2.4-4% nitrogen, 0.1-0.7% phosphorus, 2-5% potassium, 0.2-4% calcium, 0.3-2% magnesium, 100-250 ppm iron, 50-250 ppm manganese, 30-70 ppm zinc, 5-25 ppm copper, 20-50 ppm boron.

Managing Disease, Pests and other problems : 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, a broad-spectrum fungicide, or you can 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, Truban WP and Truban EC. Check with manufacturers regarding compatibility when tank mixing fungicides for Pythium with Rhizoctonia or 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 in bud. Many chemicals are listed for aphid control, including, Safari, Celero, Flagship, Tristar, Marathon, DuraGuard, Distance, Enstar II, Preclude TR, Tame, Thiodan smoke, 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 on 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. Not that registration of pesticides varies by state so consult and follow labels for registered uses. To avoid any potential phytotoxicity or residue problems, spot test first before widespread use. No discrimination is intended for any products not listed.

Leaf yellowing can develop gradually in the greenhouse or suddenly and severely after lilies are sold. Gradual leaf yellowing can be a sign of chronic stress due to a persistent and unfavorable environmental condition, or a telltale symptom of a diseased root system. Improper nutrition, poor media aeration, and low light and poor air movement from tight plant spacing, are conditions that are conducive to leaf yellowing.

Sudden and severe leaf yellowing at the end of the crop is most likely to occur on lilies in poor root health, and a poor nutritional and carbohydrate status at harvest. Prolonged cold storage prior to shipping and poor shipping conditions can also favor sudden, catastrophic yellowing.

To prevent early- and mid-season leaf yellowing (from 7-10 days before visible bud until 7-10 days after visible bud), spray Fascination at 10/10ppm. (Note: Fresco and Fascination are similar PGR formulations, both contain two active ingredients and recommendations are provided in a format that reflects the concentration of each). Apply only to lower leaves and cover thoroughly. To prevent late-season leaf yellowing and post-harvest flower senescence, spray 100/100ppm to thoroughly cover all foliage and buds. Apply when buds are 3 to 3 ½” long & NOT MORE than 14 days before shipping or cooling to protect leaves from yellowing for up to 14 days. Side effects include increased stem stretch so avoid contact with immature leaves during early- and mid-season applications. However, growers sometimes spray these compounds at 3-5ppm at 7-day intervals or as needed to increase stem stretch.

Getting Ready to Ship: Lilies require adequate fertilization from planting to finish but high salts in shipping could be a problem. Apply one clear watering right before shipping to lower salt levels and enhance the keeping quality for the consumer.

Good quality lilies can deteriorate rapidly after they leave the greenhouse if they are not shipped properly. Avoid holding sleeved and boxed lilies for long periods of time, especially when temperatures are high in the shipping container. EthylBloc can also be used to increase post-harvest flower life. EthylBloc works by inhibiting the damaging effects of ethylene (a naturally occurring plant hormone that greatly accelerates the onset of flower aging and death). Plants produce ethylene naturally but ethylene can also result from the incomplete combustion of fuels in a greenhouse, shipping, or warehouse environment.

The active ingredient in EthylBloc, 1-methylcyclopropene or 1-MCP, is released as a gas and therefore lilies must be treated in an enclosed environment. A sealed shipping container or truck, or sealed greenhouse can be used to treat plants. Flowers must be fully developed before treatment. To extend flower-life, treat lilies with EthylBloc just prior to harvest, or immediately after harvest, or just prior to shipping, or upon arrival from a supplier, or just prior to sale. Note that repeat applications are not harmful and are recommended on species such as lily that bloom sequentially over time.

There’s no question that the 2008 schedule will be a real challenge for even the most experienced growers. How big a challenge will depend on when the bulbs arrive and of course we won’t know this until the digging season is complete. Growers should anticipate an extremely tight schedule in 2008 and the need to cut a few corners to make this crop. Before the season starts, make sure your insurance lighting system is ready to go and decide where in the schedule you want to cheat for time. Once started, stay on top of crop development by tracking leaf unfolding and bud development. You don’t want to fall behind too far or you may not be able to catch up. Just to make you feel better, 2008 is a leap year so you do have one extra day. Good luck and have a profitable Easter in 2008.