PGR Guidelines for Greenhouse Production, courtesy of Purdue Extension
Use products only as labeled. The labels indicate:
• Any known intolerances.
• Application timing.
• Any phytotoxic effects.
General Recommendations
• Use higher concentrations of PGRs when plant growth rates are high (due to high temperature and light).
• Know that plant response varies with plant species and cultivar.
• Mix and apply PGRs the same day.
• Do not apply PGRs to stressed plants.
Sprays
• Repeat applications at lower rates may be beneficial (except dikegulac-sodium).
• Make sure foliage is dry before application.
• Apply 2 qts/100 ft2 spray volume (general recommendation) — chlormequat chloride and paclobutrazol may
require 2–3 qts/100 ft2 for larger plants.
Drenches
• Make sure substrate is moist, not wet — water before application.
• Decrease rates for sub-irrigation — substrate should be as moist as after a normal watering.
• Remember that as the percentage of pine bark in substrate increases, the effectiveness of ancymidol, flurprimidol, paclobutrazol, and uniconazole decreases.
Test these products first with non-composted organic substrate components.
Container Sizes and Volumes for Drench Applications
|
Container Diameter |
Drench Volume (fl oz./container*) |
Drench Volume (mL/container) |
| 4 | 2 | 59 |
| 5 | 3 | 89 |
| 6 | 4 | 118 |
| 8 | 10 | 296 |
| 10 | 25 | 739 |
| 10-inch basket | 15 | 444 |
*Chlormequat chloride rates are 3,4,6, and 8 fl oz. per 4-,5-,6-, and 8-inch containers, respectively.
More PGR information is available in Commercial Greenhouse and Nursery Production: Applying Plant Growth Retardants for Height Control, Purdue Extension publication HO-248-W. Available from the Purdue Extension Education Store, www.the-education-store.com.