What is Trimtect?

The Science of Trimtect and How to Apply

The active ingredient in Trimtect is a molecule called paclobutrazol. The molecule is part of a highly active group of plant growth regulators and fungicides known as triazoles. Widely used for decades for tree care and in vegetation management, paclobutrazol consistently reduces the shoot growth of plants by 30-70% during the growing season.

Paclobutrazol achieves growth reduction without deforming the plant or causing phytotoxic reactions seen with other growth regulation products.

How It Works

When Trimtect is applied, a lone electron on a nitrogen atom reacts with the enzyme kaurene oxidase. This interaction blocks a key step in the formation of gibberellic acid, resulting in the reduction of vegetative growth.


Plant Benefits

Energy, in the form of carbohydrates, is produced by photosynthesis and supports all metabolic processes of plant life. Energy not being spent on vegetative growth gets allocated to other areas such as defense compounds and fine root development, resulting in a number of plant health benefits.

Improved Drought Tolerance

Improved Drought Tolerance

Gibberellins (GA) and absicic acid (AA) are made from some of the same base compounds. Reducing GA results in increased AA. AA is used by plants to open and close their stomates, allowing them to respond to drought conditions and reduce their water loss. As a result, in increasingly strained irrigation periods plants require less water.

Improved Appearance of Flowering

Before and After Trimtect Treatment
Knock Out Roses

Reduced Branch Elongation


Darker Greener Leaves

Darker Greener Leaves

Improved Disease Resistance
Improved Disease Resistance

Untreated Sumac is covered with powdery mildew.

How to Apply

Trimtect can be applied by foliar spray or by basal drench. Trimtect is applied as a foliar spray to reduce application time and ensure targeted growth reduction. As a foliar spray application, the mulch, pine straw, or other organic matter don’t need to be removed prior to application thereby reducing application labor.

Foliar Spray

Foliar Spray

Basal Drench

Basal Drench

Foliar Application Steps

Applying Trimtect is quick and easy. There are 3 major steps involved.

Each plant species responds differently to Trimtect. Predictable results are only possible by properly identifying the target plant. Regional plant guides and other materials are available to aid your crews.

Once the plant species is identified, determine the proper amount of product needed by referring to the Trimtect label or Shrub Dosage Chart in the Trimtect Application Guide. Using the square footage of the shrub, follow the rates on the product label. Once the rate is determined, make the ready-to-use solution in your spray tank.

Apply the ready-to-use solution to the shrub. One gallon of mixed, ready-to-use Trimtect will typically treat 200 – 400 ft2. Ensure that the foliage, canopy, and all interior stems of the plant are thoroughly covered. Trimtect should be applied as a spray-to-drip application.


Keys to Successful Foliar Applications

  • Trimtect should be applied as a spray-to-drip application.
  • Coverage is important as Trimtect is only locally systemic.
  • Plants with adventitious buds located on the interior of the plant should be sprayed thoroughly.
  • Remove any debris that may interfere with a spray application.
  • Ensure the foliage, canopy, and all interior stems of the plant are thoroughly covered.

Optimal Application Conditions to Minimize Evaporation
Low light, low wind and high humidity

Mix Rate Information
Because certain plant species respond differently to Trimtect, Rainbow has spent years developing precise rates for each species of shrubs. Shrub species fall within 1 of 3 groups (A, B, or C). These groups correspond with how much Trimtect to mix. In order to get effective control without over or under regulation, follow the Trimtect rates.

Here are a few examples of common species and their mix rates:

*Refer to the Trimtect label for more species
LABEL RATE 1.6 oz.of TrimtecT /
1 gallon of water
3.2 oz. of Trimtect /
1 gallon of water
6.4 oz. of Trimtect /
1 gallon of water

For more species, refer to the Trimtect label.

Application Timing

Trimtect is unique in that you can make applications throughout the growing season and get growth control. Whether your clients’ prefer a manicured or natural appearance, Trimtect can help you achieve those results for much longer.

Manicured Appearance
Some property owners want to maintain a specific manicured look throughout the season. Timing when you apply Trimtect can help maintain this look for much longer. For dormant shrubs, in order to maintain a manicured appearance, apply Trimtect just after bud break and leaf expansion. During the growing season, apply Trimtect within 1 – 2 weeks after trimming.

Natural Appearance
In order to maintain a more natural appearance, apply Trimtect when the shrub or hedge has reached the desired appearance. Trimtect will start to slow the growth of the plant within 1 – 2 weeks after application.

Comprehensive Trimtect Training Is Available!

Proper training of applicators and account managers is critical for ensuring success. RTSA is capable of providing training materials, hands- on application training, and other necessary educational material to train staff for success.

Contact your Territory Arborist or the Solution Center to schedule training for your crews.

Technical Support:

  • In–field application training
  • Online training
  • Diagnostic training
  • Live phone support from ISA certified arborists
  • Regional technical representatives

Solution Center: 1-877-272-6747