A Review of Literature Involving the Use of Growth Regulators to Induce Flowering of Tropical Foliage Plants

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University of Florida, IFAS
Central Florida Research and Education Center - Apopka
CFREC-Apopka Research Report, RH-90-11

R.J. Henny*

Introduction: This report presents a summary of published literature concerning the use of growth regulators to induce flowering of foliage plants. The information in this report is intended to be a reference for anyone interested in flowering foliage plants.

Two reasons for inducing flowering of foliage plants are: 1) to increase the salability of a particular plant that has attractive flowers (i e. Bromiliads, Spathiphyllum and Zantedeschia); and 2) to obtain flowers, that may or may not have any ornamental value, for breeding purposes (i.e. Aglaonema, Dieffenbachia and others in this report). Only two chemicals have been utilized to induce flowering of foliage plants; they are gibberellic acid (GA3) and ethrel (ethephon). The results of this literature review are summarized in Table 1.

Summary of Literature

Aqlaonema (ref. #6) - Aqlaonema flowers have no ornamental value and become a nuisance once they begin to die and decay on the plant. However, the use of GA3 as a treatment for simultaneous flower induction is imperative for breeding purposes. A single foliar spray with 250 ppm GA3 has consistently induced flowering and increased flower number in many species and cultivars. The time from treatment to blooming is about 4-5 months.

Bromeliads (ref. #13) - Studies with Aechmea, Guzmania and Vriesea showed that 25 mg of ethephon applied to the vase of these bromeliads, 1.5 to 2 years old at the time of treatment, should induce flowering within 2 months without damaging leaves.

Twenty-five mg of ethephon can be obtained by mixing one tablespoon (15 ml) of 21.3% ethrel in one gallon (3.8 liters) of water and adding 2 tablespoons (30ml) of this solution to the vase of the bromeliads. In the above study the vases contained water from overhead watering the day before treatment, so it is not necessary to drain existing water from the vases before applying the ethephon.

Caladium (ref. #3) - Tubers, removed from storage, then soaked for 8 or 16 hours in 250 ppm GA3 flowered approximately 65 days. These results are important for breedlng purposes.

Cordyline (ref. #2) - Terminal inflorescences of Cordyline terminalis appeared 4-6 weeks after apical buds were treated with GA3 or GA4+7. Optimum flowering required application of 0.12-0.15 ml of 500 ppm GA3 or GA4+7 applied to the apical bud. These results are mainly of value to breeders.

Dieffenbachia (ref. #4) - The ability to routinely flower Dieffenbachia species and cultivars simultaneously has made breeding much easier. This is accomplished by a single foliar spray with 250 ppm GA3. Flowers normally mature within 3-4 months following treatment.

(ref. #7) - Tetraploid breeding lines have proven more difficult to flower using GA3 sprays and require higher treatment rates than normal diploid plants. Even at rates of 500 ppm only 30-80% of tetraploid plants flowered compared to 100% of diploids.

Ficus (ref. #11 and #12) - Application of 500 mg ethephon to Ficus benjamina liners in 2-gallon pots stimulated flowering and fruit set. However, root and top growth was severely reduced and top growth became prostrate rather than vertical. These results may be of value to someone interested in breeding Ficus.

Homalomena. (ref #10) - Homalomena lindenii plants were stimulated to flower with a single foliar spray to runoff with 100, 200 or 400 ppm GA3. Treated plants flowered within approximately 140 days. All treated plants averaged 10-11 flowers while untreated plants did not bloom. In a second test, plants sprayed with 25, 50, 75 or 100 ppm GA3 produced an average of 8-9 flowers per plant 4 months after treatment whereas those treated with 0 or 10 ppm did not flower. These results are of value for breeding purposes only since the flowers have no ornamental merit.

Spathiphyllum (ref. #5) - The ability to induce flowering of Spathiphyllum with GA3 was first reported in 1981. Spathiphyllum 'Mauna Loa' seedlings flowered after receiving a single foliar spray of GA3 at 250, 500 or 1000 ppm. Most treated plants had visible buds or open blooms within 12-14 weeks after treatment. In that study approximately 15% of the inflorescences exhibited distortion consisting of either curved peduncles or spathes with extra appendages.

(ref. #8) - In this study four Spathiphyllum cultivars were given a single foliar spray with 250 ppm GA3 during August. The cultivars tested included Tasson, Wallisii, Queen Amazonica and Bennett. All four cultivars flowered readily in response to GA3 treatment. Treated 'Bennett' and 'Wallisii' plants had open blooms within 9 weeks of treatment. 'Tasson' and 'Queen Amazonica' required approximately 2 weeks longer to flower. Overall flower quality was good for 'Bennett' and moderate for 'Tasson' and 'Queen Amazonica'. 'wallisii' produced poor quality flowers.

(ref. #9) - Spathiphyllum 'Starlight' was treated with a single foliar spray of GA3 at 0, 125, 250 or 375 ppm in March. All treated plants had good quality flowers at 15 weeks after treatment while no untreated plants bloomed. GA3-treated plants were slightly taller and had new leaves that were narrower than untreated plants. It was concluded that Spathiphyllum 'Starlight' would be a good cultivar for GA3-treatment.

Zantedeschia (ref. #1) GA3 was applied to calla lily at 0, 50, 100, 500 or 1000 ppm as a 10-minute preplant rhizome soak or as a foliar spray. Soaking rhizomes in 500 ppm GA3 prior to planting increased number of flowering shoots and flowers per shoot. Leaf width was narrower on treated plants but length was not affected. Foliar sprays were applied when the first leaf was unfolded on one-half of the plants. However, they were generally not effective.

Table 1. A summary of growth regulators used to induce flowering of foliage plants.
Method of application
Aglaonema GA3 250 ppm a single foliar spray to runoff
Aechmea Ethrel 25 mg poured into plant's vase
Caladium GA3 250 ppm tuber soak for 8 or 16 hours
Cordyline GA3 500 ppm 3 drops on 3 consecutive days to the newest unrolled leaf
Dieffenbachia GA3 250 ppm a single foliar spray to runoff
Ficus Ethrel 500 ppm soil drench
Guzmania Ethrel 25 mg poured into plant's vase
Homalomena GA3 100 ppm a single foliar spray to runoff
Spathiphyllum GA3 250 ppm a single foliar spray to runoff
Vriesea Ethrel 25 ppm poured into plant's vase
Zantedeschia GA3 500 ppm 10-minute rhizome soak

*Professor of Plant Genetics, Central Florida Research and Education Center - Apopka, 2807 Binion Road, Apopka, Florida 32703-8504

Literature Cited

1. Corr, B.E. and R.E. Widmer. 1987. Gibberellic acid increases flower number in Zantedeschia elliottiana and Z. rehmannii. HortScience 22(4):605-607.

2. Fisher, J.B. 1980. Gibberellin-induced flowering in Cordyline (Agavaceae). Journal of Experimental Botany 31(122):731-735.

3. Harbaugh, B.K. and G.J. wilfret. 1979. Gibberellic acid (GA3) stimulates flowering in Caladium hortulanum Birdsey. HortScience 14:72-73.

4. Henny, R.J. 1980. Gibberellic acid (GA3) induces flowering in Dieffenbachia maculata 'Perfection'. HortScience 15:613.

5. Henny, R.J. 1981. Promotion of flowering in Spathiphyllum 'Mauna Loa' with qibberellic acid. HortScience 16:554-555.

6. Henny, R.J. 1983. Flowering of Aglaonema commutatum 'Treubii' following treatment with gibberellic acid. HortScience 18:374.

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) CFREC-Apopka Research Report RH-85-3.

9. Henny, R.J. and W.C. Fooshee. 1988. Floral induction in Spathiphyllum 'Starlight' with gibberellic acid treatment. CFREC-Apopka Research Report RH-88-17.

10. Henny, R.J. 1988. Inducing flowering of Homalomena lindenii (Rodigas) Ridley with gibberellic acid. HortScience 23:711-712.

11. Johnson, C.R. 1979. Influence of growth regulators on Ficus benjamina L. Nurserymen's Digest. 13(5):88.

12. Johnson, C.R. and J.N. Joiner. 1978. Influence of ancymidol and ethephon growth of Ficus benjamina L. Proc. Fla. State Hort. Soc. 91:204-205.

13. Poole, R.T. and C.A. Conover. 1975. Flowering of bromeliads. Florida Foliage Grower 12(6):1-2.