The 2009 ASHS Annual Conference

Poinsettia production requires considerable labor to pinch the crop. This study evaluated plant growth regulators (PGRs) as an alternative to a manual pinch. ‘Early Cortez’ and ‘Mars Red’ cuttings (Syngenta Flowers, Boulder, CO) were potted into 15cm azalea pots in Sunshine Mix 1 on 22 August, 2008, and grown under long day conditions until 1October. Treatments were arranged in a completely randomized design with 5 replications and were applied on 10 September. Treatments included a pinched control, a non-pinched control, 6-benzylamino-purine (BA); 40, 80, 120 mg·L^-1; Configure™; Fine Americas, Walnut Creek, CA), Cyclanilide (10, 20, 30 mg·L^-1; Bayer Environmental Science, Research Triangle Park, NC), and BA/Cyclanilide tank mix (40/10, 40/20, 40/30, 80/10, 80/20, 80/30, 120/10, 120/20, 120/30 mg·L^-1 ). B-Nine/Cycocel (2,500/1,500 mg·L^-1; Chemtura Corp. Middlebury, CT /OHP, Inc., Maryland, PA) was sprayed on 10 October for height control. Data was collected on plant height, width, and inflorescence diameter of the top three inflorescences on 16 December. All the PGR treatments produced taller plants than the pinched control except 20 mgL^-1 Cyclanilide and 40/30 mgL^-1 BA/Cyclanilide on ‘Mars Red’. No PGR treatment had an effect on plant width of either cultivar. On ‘Early Cortez’, all the treatments except 40/30 mgL^-1 BA/Cyclanilide produced a larger terminal inflorescence compared to pinched treatment. All the PGR treatments produced significantly larger secondary inflorescences than pinched treatments except Cyclanilide alone or 40/10 mgL^-1 BA/Cyclanilide. All the PGR treatments produced smaller tertiary inflorescences compared to pinched treatment. On ‘Mars Red’, all the PGR treatments had similar sized inflorescences compared to pinched treatment.