Section 6: Other Benefits With the Application of Plant Growth Regulators
Because of how some plant growth retardants inhibit the production of gibberellin, there are a few other beneficial biochemical processes magnified in the plant. The application of plant growth retardants increase the concentration of chlorophyll in the plant, which results in darker green foliage. Darker green plants typically have greater consumer appeal.
Along with the more compact growth that occurs with the application of plant growth retardants, there is also a decrease in water use. Thus, in areas where water conservation is a concern, plant growth retardants might be considered a best management practice.
Originally, many of the plant growth retarding chemicals were discovered in fungicide efficacy trials. Therefore, it is not surprising that a few of them (flurprimidol and paclobutrazol) have demonstrated fungicidal activity. This disease protection is an added benefit of using certain plant growth retardants.
Mixing Plant Growth Regulators
When mixing plant growth regulators, great care needs to be given to accurately measuring and applying the chemical. Drench applications vary by pot size and desired dose, so refer to the product label for exact mixing instructions. As always, the label contains the legal mixing information.
Correct Dosage
In order to achieve the desired effect on plant growth, a known dose needs to be applied to each plant. The dose to apply to a crop is based on two factors: (1) the solution concentration and (2) volume of solution applied per area or per plant.
Foliar sprays require an even application to obtain consistent results. To accomplish this, a dose is based on measuring out a known amount of chemical and adding it to a known volume of water to achieve the desired concentration. Next, the foliar spray needs to be applied to a known area. Most foliar sprays are applied at the rate of 2 quarts per 100 square feet. Applying this known concentration over a known area provides a known dose per plant.
Drench applications are based on measuring out a known amount of chemical and adding it to a known volume of water. This provides a solution with a known concentration. Next, the solution must be applied at a specific volume of drench solution to each plant or pot. Applying this known concentration with a known amount per pot provides the desired dose per plant. The volume of drench applied increases with the pot size (specifics are listed on each product label). For instance, 2 oz of drench solution should be applied to a 4-inch pot, 3 oz to a 5-inch pot, 4 oz to a 6-inch pot, and 10 oz to an 8-inch pot.
How well do the plant growth regulators work? The only way to confirm the efficacy of a plant growth regulator is to leave a few representative plants untreated. These “check plants” offer a valuable insight into ways to adjust future plant growth regulators applications.
