Weekly Growth and Development of 40 Poinsettia Cultivars

Paul Fisher, Associate Professor and Extension Specialist, Dept. of Plant Biology, University of New Hampshire, Durham, NH 03824, e-mail Paul.Fisher@unh.edu. © University of New Hampshire, 2002.

Every fall as the sales date approaches, growers ask whether their poinsettia crop is ahead or behind in flower development. To help address this question, we grew 40 Paul Ecke Ranch cultivars at the University of New Hampshire (UNH) during 2001 and tracked their flower development with weekly photographs.

Figures 1. Weekly growth and development of Prestige Red. Numbers above the photograph represents weeks after start of short days (on Sept. 25 using black cloth). The asterisk (*) represents anthesis (pollen shed).

Figure 1 shows photos for Prestige Red. To view any of the 40 cultivars, select the cultivar name from the list at the bottom of this web page.

Plants were grown in a computer-controlled glass greenhouse in 6-inch pots, with 69.5^oF night and 68.5^oF day (20.8^oC/20.3^oC), giving an average daily temperature of 69^oF (20.6^oC). Plants were lit with incandescent lights from 10 p.m. to 2 a.m. until Sept. 25, then black cloth was pulled from 5 p.m. until 8 a.m. until Oct. 15, followed by natural day lengths.

These growing conditions are important in order to relate our photos to your greenhouse crop. Poinsettias grown under natural days often take several days longer to flower than plants grown with black cloth. Greenhouses in the Southern U.S. also experience high night temperatures (heat delay), which delays first color on bracts compared with UNH conditions.

If your temperatures (averaged over 24 hours) are cooler than the 69^oF in our trial, then the crop will flower later and you need to adjust the weeks from short days to flower as shown in Table 1. For example, Freedom White flowered after 7 weeks at UNH at 69^oF, but would take 8 weeks if the greenhouse temperature averaged 66^oF (e.g. 69^oF day/63^oF night).

Table 1. Effect of different air temperatures (averaged over 24 hours) on the weeks from short days to flower, based on research by Dr. Royal Heins at Michigan State University. For example, if a crop took 8 weeks to flower at UNH at 69^oF, it would take approx. 9 weeks at 66^oF.

Average daily temperature	Weeks from short days to flower
63oF (17.2oC)	9	10	12	13
66oF (18.9oC)	8	9	10	11
69oF (20.6oC)	7	8	9	10

Click here to download all photos in PDF format (5.1 Mb, requires fast connection), or select a cultivar name below to see weekly flower development photos:

Amazon Peppermint Candy Cane Freedom Bright Red Freedom Fireworks Freedom Jingle Bells Freedom Marble Freedom Pink Freedom Red Freedom Rose Freedom Salmon Freedom White Holly Point Jester Red Jingle Bells Monet Twilight Monet Peterstar Marble Peterstar Orange Peterstar Pink Peterstar Red

Peterstar Silverbells Peterstar White Plum Pudding Prestige Red Red Satin Red Splendor Red Velvet Snowberry Punch Snowcap Strawberry and Cream Strawberry Punch Success Coral Success Light Pink Success Red Supjibi Red Winter Rose Dark Red Winter Rose Deep Pink Winter Rose Jingle Bells Winter Rose Pink Winter Rose White

Acknowledgements: This research was funded by the Paul Ecke Ranch, the UNH Agricultural Experiment Station, and the Anna and Raymond Tuttle Environmental Horticulture Fund. Linda Bilodeau, Camille Esmel, Debbie Row and Brandon Smith assisted with the experiment, and web design was by Faye Cragin of UNH Cooperative Extension.