Saturday, November 10, 2007

Greenhouse - Use of Fascination on Poinsettias

There are several tools to control plant height in poinsettias. However, some of the growth regulators can reduce bract size. The following is a report on research using Fascination, a hormone product that can maintain good bract size and can be used to counteract the effect of excess growth regulators.

During poinsettia production various plant growth regulators (PGR’s) are typically used to control stem elongation. A potential negative side effect of PGR usage is the reduction of bract size. This is especially possible when PGR’s are applied late in the season or when an overdose occurs.

Fascination (Valent USA) is the brand name of a product that has been available for many years and is composed of the naturally occurring plant hormones, gibberellins and cytokinin. A couple of years ago this material received an EPA label registration for use on poinsettia crops. It has proven to be an effective material for increasing poinsettia stem elongation and bract size, especially after an overdose of a PGR. It also provides a counteracting option for those growers who have the tendency to produce consistently short and compact poinsettia crops each year. The objectives of the Michigan State University experiments were to determine the effects of Fascination rates and timing on poinsettia stem elongation and bract area size. In addition, a study was performed comparing the affects of Fascination applications to poinsettia plants provided with and without a Bonzi (growth retardant) drench.

Experimental Conclusions

Poinsettia growers can increase plant height by 1 to 2 inches by spraying a single application of Fascination at the 3 to 5-ppm rate. Maximum plant height increases are achieved when sprays are timed 7 to 10 days after initial bract color is observed. This spray timing will also promote some increase in bract area. To achieve the greatest increase in bract area size, spray Fascination 20 to 30 days after initial bract color. This later spray timing results in limited stem elongation.

Important Precautions to Consider

The optimum Fascination rates and timing depends on desired expectations and specific physical and environmental factors. Various cultural practices including temperature, light conditions, potting media, fertilization and watering will all affect the final impact from different Fascination spray rates. Dissimilarities in response can also occur with different poinsettia varieties. To determine optimum use rates, conduct trials on a small number of plants under actual use conditions using the lowest indicated rate.

The application of Fascination to poinsettia during the period of time between start of short days to two weeks after first bract color can promote delayed coloration. Therefore, increased bench time can postpone proposed shipping dates. Furthermore, when Fascination increases bract expansion the dilution of leaf pigmentation causes the color of bracts to appear lighter. As bract maturity continues to develop with time the color will also improve. However, often times the treated bracts will never reach the same dark coloration as non-sprayed plants. Multiple applications will exacerbate the lightening of bract color.

Extracted from the "Greenhouse Research Summary" by Steven K. Rettke, Rutgers Cooperative Extension in the January 2007 edition of the Northeast Floriculture IPM Notes from Rutgers and Cornell Universities.

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