Flowering of Ornamental Aroid Genera with Gibberellic Acid

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University of Florida/IFAS
Institute of Food and Agricultural Sciences
Central Florida Research and Education Center

CFREC-Apopka Research Report RH-96-11

R. J. Henny and T.A. Mellic*

Attractive foliage makes aroid genera such as Aglaonema, Dieffenbachia, Homalomener and Syngonium popular, while genera such as Anthurium, Spathiphyllum and Zantedeschia are valued for their beautiful flowers. Whether flowers are used as a sales tool or in breeding, the ability to stimulate aroids to bloom is an important technique. Fortunately, research has shown that application of the plant growth regulator, gibberellic acid (GA₃), to aroids will induce flower production. This paper summarizes the most current information relating to use of GA₃ for stimulating flowering of nine genera of ornamental aroids.

Aroids can be induced to flower by treatment with GA₃, which can be purchased in a liquid formulation (Gib-Gro, 4% GA₃, Agtrol Chemical Products, Houston, Texas). A single foliar spray is the easiest method of applying GA₃ and works well. A wetting agent should be added to the treatment solution to aid in coverage and the foliage should be thoroughly covered until runoff. A tuber soak for Caladium and a rhizome soak for Zantedeschia were also effective treatment methods. A general treatment concentration range is between 250-500 ppm (1 ounce of Gib-Gro per gallon of water = 250 ppm GA₃). The response to GA₃-treatment of these and other aroid genera are summarized in Table 1.

Under Florida growing conditions, different aroid species within a genus may flower unpredictably. For example, most Aglaonema and Dieffenbachia species flower in late winter and early spring; however, some species consistently flower at other times of the year or not at all. Inability to flower species simultaneously is a major hurdle in breeding studies and can hinder sales of genera whose flowers are a sales asset. Flowering of Spathiphyllum with GA₃ treatment originally was for breeding purposes, but this discovery soon led to development of a production system whereby growers could use GA₃ to ensure a supply of flowering plants throughout the year. On the other hand, forced flowering of Aglaonema and Dieffenbachia is only for breeding since their flowers have no ornamental value.

Generally, GA₃-treated plants produce more flowers compared to natural flowering. This effect is particularly evident in Aglaonema and Dieffenbachia where flower counts on treated plants may double those obtained from natural flowering. In addition, higher GA₃ rates generally yield more flowers than lower rates.

Time from treatment to the presence of open flowers may range from 7 weeks for Caladium to 20 weeks for Aglaonema and Homalomena. However, most genera flower within 12-15 weeks of treatment (Table 1). These intervals are only approximate and will vary significantly depending on the season. Plants treated during the summer flower faster in response to GA₃ than those treated in winter. For example, GA₃-treated Spathiphyllum 'Petite' may flower in 8-10 weeks in the summer but the same cultivar may require 16-20 weeks to flower in the winter depending on the minimum temperature range. In general, the faster a plant's growth rate the faster its response to GA₃ treatment. Different species and cultivars within a genus generally flower together if treated simultaneously with GA₃. No detrimental effects to fertility have been observed due to GA₃ treatment.

Plants treated with GA₃ tend to produce narrower leaves for a period following treatment. In Spathiphyllum, some flower distortion may occur, the extent of which varies with cultivar. GA₃ treatment has proven to be a reliable method to stimulate flowering of several ornamental aroid genera. It is currently used regularly to allow nurserymen to produce a continual supply of blooming Spathiphyllum. The other major role of GA₃ will remain as an aid to plant breeding efforts in ornamental aroid genera.

*Professor of Environmental Horticulture and Biological Scientist, University of Florida, IFAS, Central Florida Research and Education Center, 2807 Binion Road, Apopka, FL 32703, respectively.

Additional References

1. Corr, Brian E. and Richard E. Widmer. 1987. Gibberellic acid increases flower number in Zantedeschia elliottiana and Z. rehmannii. HortScience 22(4):605-607. Harbaugh, B.K. and G.J.
2. Wilfret. 1979. Gibberellic acid (GA₃) stimulates flowering in Caladium hortulanum Birdsey. HortScience 14(1):72-73.
3. Henny, R.J. 1980. Gibberellic acid (GA₃) induces flowering in Dieffenbachia maculata 'Perfection'. HortScience 15(5):613.
4. Henny, R.J. 1981. Promotion of flowering in Spathiphyllum 'Mauna Loa' with gibberellic acid. HortScience 16(4):554-555.
5. Henny, R.J. 1983. Flowering of Aglaonema commutatum 'Treubii' following treatment with gibberellic acid. HortScience 18(3):374.
6. Henny, R.J. 1988. Inducing flowering of Homalomena lindenii (Rodigas) Ridley with gibberellic acid. HortScience 23(4):711-712.
7. Henny, R.J. 1989. Floral induction in 2n and 4n Dieffenbachia maculata 'Perfection' after treatment with gibberellic acid. HortScience 24(2):307-308.
8. Henny, R.J. and W.C. Fooshee. 1985. Inducing flowering of four Spathiphyllum cultivars with gibberellic acid (GA₃). AREC-A Research Report RH-85-3.
9. Henny, R.J. and R.L. Hamilton. 1992. Flowering of Anthurium following treatment with gibberellic acid. HortScience 27(12): 1328.

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