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Poinsettias Need Darkness for Color

News Article for September 26, 2011:

It seems a little early to be planning for Christmas, but if you want that poinsettia that you saved last year to have color you will need to take action soon.

Poinsettias have a photoperiod requirement to satisfy for them to show color. This is controlled by the amount of dark hours they receive and then bright sunlight in the daytime. We have about 12 hours of daylight day now and 12 hours of darkness, which would probably bring about color if there were no artificial lights around to break that dark period.

Commercial growers of poinsettias will usually start about October 5 -12, inducing a controlled dark period, which will initiate color on the bracts or modified leaves. Each grower has his or her own method but they usually will have about 40 continuous days with a darkness period of 13-14 hours daily. This is usually done in a green house with shade cloth and no outside lights around.

Providing darkness for poinsettias is much harder for the homeowner because most of us live in areas with security lights outside and in areas where car lights will shine as people enter and exit the driveway.

One method that some people have used successfully is to put the plant in and out of a closet or outbuilding daily. It has to be in a room where the door will not be open during the night and you have to seal out light from the cracks around the door. You will also need to take the plant in and out daily so it gets the sunlight and energy that it needs.

Each day that you interrupt the dark period of the poinsettia will delay the onset of color. Many growers have had mishaps that delayed the crop, sometimes past the Christmas season. Even an electrical storm with lightning can cause a delay.

For more information on these or related topics contact Kenny at 225-686-3020 or visit our website at

Last Updated: 10/1/2012 9:42:26 AM

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