Poinsettias cultivars can take cooler temperatures, save energy for growers

October 9, 2012 by Brian Wallheimer
Roberto Lopez found that poinsettia growers can lower greenhouse temperatures to finish the plants, but they'll need to start them a little earlier than usual. Credit: Ariana Torres

(Phys.org)—Growers who carefully select their poinsettia cultivars can lower their greenhouse thermostats in mid-October to save on energy costs and produce high-quality plants, according to a Purdue University and University of New Hampshire study.

Roberto Lopez, an associate professor of , said that poinsettia cultivars that initiate and finish within six to eight weeks, are moderate to high vigor and have naturally large bracts that will do just fine in cooler temperatures if flower producers want to save on heating expenses. The team's findings, reported in the journal , showed that 10 red poinsettia cultivars finished under cooler temperatures simply need to be planted a little earlier to be ready for .

"Over the past 10 years, energy prices for growers have increased more than 230 percent. As a result, many growers stopped growing poinsettias or lowered their thermostats without knowing what the cultivar-specific consequences would be," Lopez said. "Now we know that they can save money by reducing finishing temperatures, but they have to plan ahead a little and work with the breeding companies to make sure they are using the correct cultivars."

Poinsettias are native to of Mexico and Central America, so growers must heat their to about 75 degrees during the day and 67 at night in order to grow the crop in the United States' temperate climate. Lopez; Diane Camberato, a greenhouse technician; and Brian Krug, an Extension specialist at the University of New Hampshire, tested at about 70 degrees and 68 degrees, and nighttime temperatures at 63 degrees and 55 degrees.

The cooler the temperatures, the longer it took for the poinsettias to reach marketability. But other than that, they were similar in size, color and other characteristics. The cultivars took anywhere from two days to three weeks longer to flower under the reduced temperatures.

Lopez said growers would need to start their poinsettias a week or two earlier in August. That would increase some production costs, but taking advantage of naturally warmer temperatures in August to promote vegetative growth would offset those costs.

"Using these reduced finishing temperatures, a poinsettia grower could save a significant amount of money on ," he said.

Growers who have already started poinsettias this year could potentially finish their plants in cooler greenhouses, assuming they are growing cultivars that can be cold-finished, Lopez said.

Explore further: New poinsettia for the nontraditionalist

More information: Development of Euphorbia pulcherrima under Reduced Finish Temperatures, Diane M. Camberato, Roberto G. Lopez, and Brian A. Krug, HortScience, 2012.

ABSTRACT
The holiday poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch.) is the number two potted flowering crop sold in the United States with a reported wholesale value of $146 million in 2010. Profitability is increasingly threatened as the cost to heat greenhouses has increased by over 90% in the last 10 years. As energy costs continue to increase and poinsettia prices remain relatively constant, growers are seeking cultivars that can be finished under reduced temperatures. Our objectives were to quantify how reduced temperature finishing (RTF) 2 weeks after the start of short days influences height, bract area index, and time to anthesis of poinsettia. Eight red poinsettia cultivars were selected based on their early response attributes (initiate and finish within 6 to 8 weeks), moderate to high vigor, and naturally large bracts. Rooted cuttings were grown at day/night temperature set points (12 h/12 h) of 24/19 ºC  until 15 Oct. and under a 16-h photoperiod consisting of natural daylengths with day-extension lighting until 1 Oct. On 15 Oct., plants were transferred to day/night temperatures (12 h/12 h) of 20/14, 21/17, or 24/19 ºC. Time to anthesis from the start of short days was 60 and 55 days at 24/19 ºC  and 76 and 68 days at a reduced finishing temperature of 20/14 ºC  for 'Prestige Early Red' and 'Early Orion Red', respectively. Final height was not significantly influenced by RTF in either cultivar. Our results indicate that RTF is a viable option that greenhouse growers can use to help reduce energy costs of carefully selected poinsettia cultivars.

Related Stories

New poinsettia for the nontraditionalist

December 7, 2006

U of I plant scientist Daniel Warnock hopes that one day soon a uniquely marbled pink poinsettia will be available to consumers who like decorating for the holidays with a flare for the unusual. The variety is yet unnamed, ...

Is transgenic cotton more profitable?

February 18, 2008

Transgenic cotton cultivars were planted on almost 93% of U.S. cotton acres in 2007. Transgenic cultivars with pest-managing traits are dual-purpose products. The cultivars produce lint and seed, while the expressed propriety ...

Plentiful poinsettias without PGRs

November 4, 2009

Poinsettias can be a lucrative crop for ornamental plant growers, particularly during the Christmas season. In the temperate regions of the southern hemisphere, where poinsettias are grown for both export and local markets, ...

Recommended for you

Shedding light on millipede evolution

August 2, 2015

As an National Science Foundation (NSF)-funded entomologist, Virginia Tech's Paul Marek has to spend much of his time in the field, hunting for rare and scientifically significant species. He's provided NSF with an inside ...

Researchers design first artificial ribosome

July 29, 2015

Researchers at the University of Illinois at Chicago and Northwestern University have engineered a tethered ribosome that works nearly as well as the authentic cellular component, or organelle, that produces all the proteins ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.