Chemical Growth Retardant Application to Scaevola

Abstract

Fan flower (Scaevola aemula L.) has become a popular specialty bedding and hanging basket plant in the United States. The genus contains several species from Australia and the Indo-Pacific region and there exists a wide diversity of growth habits and flower colors, including blue, violet, pink and white. Our objective was to measure the effect of type of growth retardant, method of application, and chemical concentration on S. aemula `New Wonder', `Mini Pink Fan', 'Purple Fan', and `Royal Fan', S. albida 'White Fan', and S. striata `Colonial Fan'. Variables measured included days to flower, plant width, flower stem number, flower stem length, and flower number per stem. Uniconazole applied as a media drench to S. aemula `New Wonder' at 1.0 and 2.0 mg·L–1 decreased plant width and flower stem length without affecting time to flower or flower number. Therefore, number of flowers per cm of stem length on S. aemula `New Wonder' was increased, resulting in attractive, compact clusters of flowers on pendulus stems. Paclobutrazol drench (4.0 and 8.0 mg·L–1) was also effective. Daminozide spray (5000 mg·L–1) reduced plant width but flower number was reduced. Ancymidol foliar sprays and media drenches (all rates) had no effect on the parameters measured. Ethephon (500 and 1000 mg·L–1) reduced plant width, but delayed flowering and reduced flower number. Uniconazole drenches were beneficial in improving the quality of S. aemula. `New Wonder' grown in hanging baskets, but the growth control was not long-lived. The effect of uniconzole on plant growth varied with Scaevola species and cultivars.