Growing poinsettias with less energy

Features - Poinsettias

Producing poinsettias under cold temperatures offers more benefits than just saving energy costs.

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August 7, 2009

At this time last year the price of oil was $150 a barrel and people were predicting the cost would rise faster than Oprah’s weight. Fast forward to this year and oil prices have been cut in half, but are on the rise again. Those growers who survived 2008 are optimistic that this year’s poinsettia season will be business as usual. I am all for optimism, but it would be unfortunate if the lessons learned about how to produce poinsettias with less energy are abandoned too quickly.

Resource conservation
The ideal approach to growing is to use the least amount of energy possible without putting crops at risk. Not only does this conserve resources, it also reduces production costs.

Many bedding plant growers are producing their crops at cold temperatures. Some of their most popular crops require cold to initiate flowering, and even more plants tolerate cold production temperatures.

Previously poinsettias were considered a warm-temperature crop that could not tolerate less than optimum conditions. What researchers and poinsettia growers have learned is growing at cold temperatures is possible, provided appropriate adjustments to schedules and culture are made. To compensate for the slower rate of growth at cooler temperatures, plants should be started and pinched one to two weeks earlier than traditional production practices.

Growing poinsettias at cold temperatures is possible provided appropriate adjustments to production schedules and culture are made.The question growers will need to answer is which requires more resources: starting a cold-temperature crop early when energy is not required, or starting the crop at the traditional time and using more traditional temperatures during October through December.

Starting the crop early will work if the greenhouses are not full to capacity in late July and early August when the majority of poinsettia cuttings are transplanted.

Which cultivars will work
During the 2006-2007 poinsettia production season, the Ecke Ranch sponsored cooperative research with universities and commercial growers in Europe and North America to document the possible energy savings available using cold temperatures. Based on data tracking, Kube-Pak in Allentown, N.J., realized a 3 percent savings for each degree in temperature lowered below 67°F. By lowering the night temperature to 60°F from the traditional 67°F, the company obtained a 21 percent savings in fuel. This resulted in a $0.07 per square foot savings based on fuel costs at the time. The fuel cost savings will vary yearly depending on weather and energy prices.

During the same year, researchers at German trial stations compared the amount of oil required to grow different poinsettia varieties. They found cultivar choice could influence how much energy was required to produce a crop.

From the start of the research the focus was to select poinsettia varieties that can be successfully adapted to cold temperature production. In the German trials, each poinsettia breeding company was asked to submit their best variety for cold-temperature growing. The results were dramatic. Varieties like Freedom Early Red required as little as 3.1 liters of oil per square meter to produce while other varieties required 4.2 liters or more. Compared to traditional temperature culture, cold temperature varieties were 35 percent more fuel efficient when grown cold. When designing a program for cold temperature poinsettias be sure to check with the breeders to confirm which of their varieties are adaptable to such a program.

Reducing the amount of energy required to produce poinsettias supports retailers and consumers increasing expectations. Producing cold-temperature poinsettias can save on both energy and water for one of the most visible and well-known holiday crops.

Keeping crops on schedule
Producing poinsettias at lower temperatures involves some risk that either the required plant height specification won’t be reached or plants won’t mature in time for sale.

With bedding plants, being a week off schedule is not as much of a concern because those plants still have the potential to be successfully sold. A week off of schedule for poinsettias can mean the difference between selling or dumping the plants. With so much at stake, the lack of predictability makes poinsettia growers nervous even before switching to low-energy production. To address this concern, the Ecke Ranch has developed easy-to-use tools for growers to visually monitor their crops to ensure they stay on schedule.

The On Target system (www.ecke.com) for height management provides a Web-based system to monitor plant growth and to decide how to manipulate height through changes in the environment and culture or through use of growth regulators.
 Poinsettias grown at cold temperatures are transplanted and pinched one to two weeks earlier than traditional crop culture. This earlier start results in the need for growth regulator applications early in the production schedule when warmer temperatures and long days encourage rapid growth. If adequate growth control is not provided during this development stage, plants can grow too tall. Also, the ability to use late-season treatments to keep plants within height specifications is greatly limited due to cold temperatures and the expected slower growth rate during October and November.
 Experience shows that little if any growth regulator treatments are required with cold-grown poinsettias after flower initiation occurs in mid- to late September. However, early growth control is critical to the success of this program. Using the On Target system allows growers to monitor and respond to plant development throughout production and keep plants to buyer specifications.

Monitoring bract color
For color development management, the Ecke Poinsettia Bract Meter (Page 35) provides a visual grid that correlates the percentage of bract color development to the number of days required to full maturity based on different temperature inputs. Starting at 5 percent bract color, growers can manage expansion and color development based on the variable temperatures and light conditions of each production season.

The Bract Meter makes it possible to adjust conditions and keep the crop on track using the least amount of energy necessary. Without using this tool, growers risk their crops falling behind in development. If this occurs, growers will then be forced to use higher temperatures, which equals more energy and higher fuel costs, to speed up development in order to meet crop sales dates. In this scenario, everything saved by growing cold is negated by the additional energy required during the coldest and darkest stage of crop development. Late forcing of poinsettias can also reduce the plant shelf life and cyathia retention; both factors that increase the amount of shrink for both growers and retailers. With a crop like poinsettias that is already marginally profitable, any additional problems that result in losses can be the difference between profitability and lost income.

To request a copy of the Bract Meter poster, contact the Ecke Ranch. A copy of the Bract Meter is shipped with the current poinsettia catalog. The back of the poster has a complete listing of the varieties proven successful for cold-growing programs.
 

For full-size graph, click here
 












Cyathia size and retention is enhanced due to the longer production cycle under cold temperatures. Prestige Early Red cyathia grown at traditional temperatures (top) and cold grown (bottom).

Other benefits
The shift to cold-temperature poinsettia production has resulted in other benefits besides saving fuel and money.

Better labor distribution. The earlier transplant and pinch dates for cold-temperature production has resulted in a better distribution of labor. Instead of having to plant all cuttings at the same time, this allows some of the crop to be started earlier, making it easier to manage work flow and reduce the peak demand for workers during late summer.

Lower phytotoxicity risk. The reduced need for growth regulator treatments after the start of short days has lowered the risk of phytotoxicity and reduced the overall amount of chemical required. Even though more growth regulator is required earlier due to the earlier start and pinch, it is applied at a time when plants are at higher density spacing so less chemical and less labor is needed. An unexpected benefit of less growth regulator applications later in production cycle is bract size. Concerns over small bracts have all but been eliminated using cold-grow programs.

The cooler temperatures that occur in October slow plant growth and the lifecycle of pests that commonly attack poinsettias. Slower development of these insects, like whitefly, makes it easier to break the cycle and gain control, enabling growers to keep the plants cleaner.

Increased bract color intensity. Bract color for red varieties becomes deeper and more vibrant with cold growing.

Better cyathia size, retention. Cyathia size and retention is enhanced due to the longer production cycle. Reduced depletion of carbohydrates late in the crop improves cyathia retention.

 

Improved postharvest life. Durability through packing, shipping and time spent at retail is enhanced due to plants being more toned and “harder,” reducing potential losses. Also, poinsettia life expectancy is extended for consumers, providing them greater satisfaction with longer-lasting poinsettias.

Planning for growing cold
Regardless of what the price of fuel will be this year, it no longer seems reasonable to produce poinsettias with any more fuel than is absolutely necessary. To be successful producing poinsettias with cold temperatures, keep in mind the following:
 

  • Select varieties proven to work under lower temperatures and keep them separate from varieties requiring more traditional culture and temperatures.  If multiple greenhouse zones are available, keep cold and warm culture varieties separated to provide the needs of each group for best results. 
  • Schedule additional growth time for cold-grow programs, starting and pinching the crop one to two weeks earlier depending on pot size and finished form. Small pots (4- to 5-inch) will require no more than one week adjustment in schedule, while larger pots will require up to two weeks more development time.
  • Adjust growth regulator programs to be more aggressive early in production and avoid any treatments if possible after the start of short days. Use the On Target program to monitor crop development and make good decisions on growth regulators or other adjustments to culture for height control.
  • Adjust irrigation and fertilizer programs for cooler temperatures. This requires keeping the growing medium drier throughout production to avoid problems with root-rot diseases and fungus gnats. The drier medium also requires higher fertilizer rate applications as the frequency of fertigation is less than traditional culture, leaving the plants at risk for nutrient deficiencies and imbalances.
  • Due to cooler root zone temperatures, do not irrigate early in the day if the water temperature further suppresses the root zone temperatures. Avoid irrigating late in the day, as this also contributes to cooling the root zone and provides conditions conducive to diseases.
  • Provide good space and airflow between the plants and keep foliage dry to avoid disease issues on the foliage and bracts.
  • Prevent insect and disease problems as is done with traditional production temperatures. However, under cooler growing conditions the life cycle of these pests is also slowed down, making it easier to get control when treatment is required.
  • Use the Ecke Poinsettia Bract Meter to monitor and adjust temperatures based on bract color development starting in October.