The 2006 poinsettia season was a strange one because there weren’t many complaints. One question asked several times dealt with energy costs and energy-efficient poinsettias. Most breeders offer varieties that can be grown cooler. Growing poinsettias cool is nothing new.
Energy-efficient varieties have been used in
Growing cool
A successful energy-efficient crop starts with variety selection, planning, quality young plant material (rooted or unrooted cuttings), ideal planting conditions and proper pinching. A critical time is the production period from planting until the beginning of short days (about two weeks into short days). This is when a strong plant with proper height and a healthy root system needs to be built.
Once Week 3 of short days (generative crop period) is reached, it is all about finishing and saving money. If you take shortcuts during the vegetative crop period, cost savings are most likely lost. The general growing practices vary slightly between a regular and a cool crop using energy-efficient varieties.
Production changes
Here are some of those differences.
Planning. Most energy-efficient varieties are low vigor and require more time to grow before the start of short days. They don’t grow much after the start of short days and don’t stretch toward the end of the crop. These are all good things that need to be considered during the planning process.
Christmas Feelings, Premium and Prestige Early Red need to be started two weeks earlier compared to more vigorous varieties. These extra two weeks are necessary to ensure height and overall plant quality.
Vegetative growing period. Don’t try to reduce costs during the wrong period. Energy-efficient varieties are not intended to be grown cool from planting on. During the first weeks after cuttings are planted until the beginning of short days, temperatures need to be 68°F-73°F days and 68°F nights.
Depending on the location of the greenhouse and the general condition, morning temperature drops can be used to control growth. Drop the temperature by 8°F-10°F two hours before sunrise until about two to three hours after sunrise. Keep the average temperature in mind to avoid stunting. Watch the dew point. When high humidity is a problem, using a negative DIF of 68°F nights and 65°F days has proven to be a better choice.
Additional plant growth regulators may be necessary, but most energy-efficient varieties have low vigor. Use good growing practices to develop a strong plant when entering the generative crop period.
Generative period. Two to three weeks into short days, slowly lower the temperatures to the recommended minimum temperatures for energy-efficient varieties. The plants won’t grow much anymore. This explains why the vegetative crop period is so important. Plants need to be strong, healthy and a good size as they enter the final production phase. Heating is not expensive during summer and early fall but becomes more costly starting in mid-October, so add size to the plants when it’s cost-effective.
Production checklist
* In general, cooler-grown poinsettias will finish a couple of days later, will have smaller bracts and darker colors (whites may turn creamy-yellow). If a crop is grown cooler than recommended, the crop might be further delayed and the bracts may be underdeveloped.
* Keep humidity below 75 percent. Space plants accordingly to keep humidity lower. Avoid dropping the temperature below the dew point, especially in humid areas.
* Keep air circulating. Regular air exchange will help to avoid Botrytis and powdery mildew.
* Use correct light levels whenever nature provides them.
* Keep greenhouse glazing clean (especially in Northern climates). Wash the roof if necessary.
* Use shade, if needed. Recommended light levels are 3,500-4,500 footcandles starting the week after pinching until mid-October; 3,000 footcandles until two weeks before shipping; and 2,000-2,500 footcandles for the last two weeks. Observe light-level recommendations for propagation, planting, pinching and spacing, as those are periods were poinsettias require less light.
* Don’t mix energy-efficient varieties with regular ones. You can grow energy-efficient varieties warmer, but it won’t work the other way around.
What will work?
Not many North American trials have been conducted to produce energy-efficient varieties in energy-efficient ways.
Varieties that do work (trialed by researchers and growers) for 6- to 6 1/2-inch pots, high-quality mass production are Prestige Early Red and the Premium series for early-season sales and the Christmas Feelings series for midseason sales. All three cultivars have similar requirements and differ most by their response time. Check with your supplier for additional energy-efficient varieties, i.e., for larger pots, and crop-specific information.
Energy-efficient cultivars
Red. Advent Red, Alreddy Fancy (variegated foliage), Alreddy Red, Autumn Red, Castor, Christmas Angel, Christmas Carol, Christmas Feelings, Christmas Spirit, Cortez Red, Early Joy Red, Early Orion, Eclipse Red, Estrella Red, Festival Red, Freedom Early Red, Freedom Red, Gala Red, Jester Red, Kris Krinkle, Mars Red, Orion Red, Premium Red, Prestige Early Red, Red Velveteen, Saturnus, Silent Night, Silent Night Crimson Red, Stargazer Red.
White. Christmas Carol White, Christmas Feelings White, Cortez White, Festival White, Freedom White, Gala White, Jester White, Mars White, Premium White, Stargazer White
Pink. Alreddy Shocking Pink, Amazing Pink, Christmas Carol Pink, Christmas Feelings Pink, Cortez Pink, Early Joy Pink, Estrella Pink, Festival Rose, Jester Pink, Mars Lipstick Pink, Mars Pink, Premium Lipstick Pink.
Novelty. Apricot Candy, Christmas Feelings Jingle, Christmas Feelings Marble, Cinnamon Candy, Cinnamon Star, Cortez Electric Fire, Da Vinci, Freedom Fireworks, Freedom Jingle Bells, Freedom Marble, Jester Marble, Mars Marble, Merry Christmas, Premium Apricot, Premium Marble, Premium Miro, Premium Picasso, Shimmer Pink, Shimmer Surprise, Stargazer Marble.
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- Stefan Reimer
Stefan Reiner is general manager at Selecta First Class Inc.; (800) 955-5644; s.reiner@firstclassplants.com; www.selectafirstclass.com.