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October 10, 2011

Plant Growth Regulator Spray Mishaps on Poinsettia

Roberto G. Lopez, Ph.D., Assistant Professor and Floriculture Extension Specialist, Purdue University

Plant growth regulator (PGRs) spray applications are very useful tools for controlling the height of vigorous poinsettia cultivars. Spraying PGRs is often the easiest, but least uniform, application method and misuse can lead to reduced bract size (Figs. 1 and 2) and/or delayed flowering. A general recommendation for growers scheduling poinsettias for early December flowering is to avoid applying PGR sprays (ie. B-Nine or Dazide) after the initiation of short days.

For those growers that have a short poinsettia crop or small bract size due to PGR misuse, Fascination can be used to help increase plant height and improve poinsettia quality (ie. increase bract size). The Fascination label can be downloaded at: http://www.valent.com/Data/Labels/Fascination2004Supplemental.pdf.

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Fig. 1. Reduced bract size in a poinsettia crop resulting from a late plant growth regulator (PGR) spray application

Fig 1. Reduced bract size in a poinsettia crop resulting from a late plant growth regulator (PGR) spray application.

Fig. 2. Excessively short poinsettia resulting from an over application of a plant growth regulator (PGR)

Fig 2. Excessively short poinsettia resulting from an over application of a plant growth regulator (PGR).

 

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service