Section 4: Other Growth Regulators Used In Greenhouse Crops Production
Not all plant growth regulators are used to control plant height. Others are used to cause flower bud abscission, increase branching, and promote flowering and shoot elongation.
Ethephon Phosphonic Acid (commercial name: Florel®). This material is absorbed by the plant tissue, and due to a change in pH once absorbed into the plant cell, it releases ethylene. Ethephon is used to promote flower bud abortion and vegetative branching in crops. Although it is used in many situations, it is most commonly used where vegetative cuttings are being produced and in hanging basket production. Ethephon is applied as a foliar spray at concentrations of 250 to 500 ppm. Ethephon may also be used to promote flowering in bromeliads.
Benzyladenine (commercial name: Configure®). Benzyladenine (BA) is used to promote branching and increase flower set. Configure ® has specific label recommendations for Christmas cactus (100 to 200 ppm foliar spray), Enchinacea (300 to 900 ppm foliar spray)and hostas (500 to 1000 ppm foliar spray) and a supplemental use label allowing for experimental applications on any annual, perennial, foliage, or tropical plant grown in a greenhouse. Optimal results occur when the plant is actively growing and is physiologically receptive for growth or flower promotion. Benzyladenine does not readily move within the plant, therefore complete coverage is required.
Gibberellins (commercial names: Florgib®, and ProGibb T&O®). Additional stem elongation may be desirable in some plants such as tree forms of azaleas, poinsettia and geraniums. For the production of tree forms of these species, the general recommendation is to apply a 50 ppm gibberellin (GA) foliar spray after plants are approximately 6 inches tall. Depending on the desired height and size, an additional one or two GA applications may be desired. Gibberellins can also be applied to promote growth and overcome over-application of gibberellin-inhibiting plant growth retardants. For this use, the general recommendation is to apply 1 to 3 ppm GA as a foliar spray and check for growth stimulation after 5 days. The application can be repeated if additional shoot elongation is desired.
Benzyladenine + Gibberellin Combinations (commercial names: Fascination® and Fresco®). These combination products are used on potted lilies as foliar sprays to avoid lower leaf yellowing and leaf drop. A typical recommendation is to apply a 25 to 100 ppm foliar spray. The actual concentration depends on timing (early versus late production applications) and species. Sprays are also beneficial at prolonging flower life of potted lilies.
