January 2012

Producing Euphorbia Hybrids for October Breast Cancer Awareness Month By John M. Dole and Ingram McCall

Fall brings to mind the rich warm yellows, oranges, bronze, reds and dark purples of tree leaves as they change color. Needless to say, pink has not been an important fall color. That began to change in 1991 when pink ribbons were handed out at a Susan B. Komen Foundation race for breast cancer awareness. Since then, pink has become identified with breast cancer survivors and support for women's health issues, especially in October, which is Breast Cancer Awareness Month.

The bright pink color of euphorbia hybrids is a natural fit for Breast Cancer Awareness month and its emblematic pink ribbon. These hybrids were produced from crosses between poinsettia and other euphorbia species and the most recent introduction, 'Luv U Pink' from the Paul Ecke Ranch, has fluorescent pink bracts with a pale edge (Figure 1, above). The plants flower naturally in the fall. However, black clothing in August would be required for early October flowering and little is known about the heat tolerance of these new hybrids. The goal was to develop a production schedule for flowering poinsettia hybrids in October and determine the interaction of production temperature and short days.

What We Did
Unrooted cuttings were propagated into Oasis foam on June 24. On July 22 rooted cuttings were planted into 61/2-inch pots with one plant per pot. At that time one half of the plants were placed in a greenhouse set at a minimum 65¡ F night (75¡ F day) and the other half at a minimum 75¡ F night (85¡ F day). Actual temperatures are listed in Table 2. Marathon was applied on Aug. 16 and 20-10-20 CLF was used throughout production. Plants were grown according to the treatment schedule in Table 1 (above left).

Our Results
Warmer production temperatures resulted in less time to first color, by two to three days for HC-59B (Table 3, Figure 2). 'Luv U Pink' did not produce anthers or pollen shed and thus, we could not collect date of anthesis for each plant. However, plants were well-colored and marketable by Oct. 4. We were not able to record anthesis on the plants, because the center bud dropped before producing pollen (Figure 3). Additional buds continued to develop, but none of them reached anthesis. However, there were many buds in the center and the loss of the center bud was not noticeable. During postharvest both bracts and buds continued to develop; however, the buds started to drop at a faster rate. After several weeks the inflorescences were still quite attractive with many bracts, despite not having center buds. Not surprisingly, previous trials have showed 'Luv U Pink' to have an excellent postharvest life.

Plants grown without Bonzi were taller, but only by 1 to 4 centimeters, than those without a Bonzi drench. Plant diameter was affected by Bonzi and schedule such that plants without Bonzi were wider than those with Bonzi when grown at 65/75¡ F.

'Luv U Pink' had bright-pink to rosy-pink bracts. An unofficial survey indicated that consumers loved the bright pink color with the thin pale edge to the bracts. Bracts were slightly lighter in color at the warmer production temperatures, but would still have been marketable as the difference was not apparent unless compared directly with plants from the cooler environment.

Our temperature control systems were not as effective as hoped and there was only a 3 to 5¡ F difference between the environments, depending on the measure used. However, the temperatures were much warmer than the indicated set points, indicating that 'Luv U Pink' could tolerate quite warm production temperatures.

Research Summary
'Luv U Pink' had bright pink color, which was not diminished by being grown in warm production temperatures. In this experiment, the use of plant growth regulators resulted in only a slight decrease in plant height. While plants could be grown with only four weeks of long days; providing five weeks of short days might be best as an insurance policy. The amount of PGR and weeks of long days required should be refined with in-house trials.

Conclusions
'Luv U Pink' made an eye-catching plant for National Breast Cancer Awareness Month. The long postharvest life ensures that consumers buying the plants will enjoy them all month long.

Producing Euphorbia Hybrids for October Breast Cancer Awareness Month