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Product Overview

OHP Pac O is specially formulated for use on ornamental plants in containers such as flowering plants, hibiscus, liners, plugs, foliage plants, azaleas, and woody plants. Contains the active ingredient, Paclobutrazol, which helps in encouraging the root growth of plants. This plant growth regulator is proven to produce no poisonous chemical to plants if used as directed. It lessens internode elongation, making plants more compact. Ideal to use on commercially grown plants in nurseries, shade houses, greenhouses, and interiorscapes. For even distribution, consistently mix the solution during application. May be used for spray or drench application. Reusing of containers that held plants treated with the product is not advisable. Available in a 128-oz. jug.

Features and Specs

Active Ingredient Paclobutrazol - 0.4 %
For use in Ornamental plants that are grown in containers in nurseries, greenhouses, shade houses, and interiorscapes.
Application Spray application must only be performed in enclosed areas. Drench applications tend to be the most effective in reducing plant height and producing a uniform effect.
Pet safe Yes, if used as directed on label.
Formulation Liquid Formula.
Special Features May be applied at any time of the day without risk ofphytotoxic effects.
Shipping Weight 9.00 lbs
Manufacturer OHP Inc.
UPC 896531002572
EPA Registration 62097-11-59807



It is a violation of Federal law to use this product in a manner inconsistent with its labeling.

Do not apply this product in a way that will contact workers or other people, either directly or through drift. Only protected handlers may be in the area during application. For any requirements specific to your State or Tribe, consult the agency responsible for pesticide regulation.

Read all label directions carefully before use.


Half fill the spray/drenching tank with clean water. Accurately measure out the required amount of PAC O. Add the PAC O to the spray tank and fill the tank with the remaining required amount of water to achieve the correct concentration.



When applying PAC O by spray, it is important that: 

  • Spray application must only be performed in enclosed areas, such as greenhouses, where spray drift outside the treated area cannot occur.
  • Sufficient volume is used to thoroughly wet plant stems.
  • Excessive spray solution is not applied as PAC O is active through both root and stem uptake. 
  • Uniform coverage of all plants is achieved.
  • A period of 30 minutes is allowed after application before overhead irrigation or rain occurs. 
  • Maximum application rates must never be exceeded.

Sequential applications using 50 to 100% of the lowest application rate can provide more uniform growth effects and also guard against overdosing. This is particularly true when cooler temperatures or lower light conditions occur. 

Generally, the spray volume for small plants in small containers or plug trays which are closely spaced is 1 to 2 quarts./100 sq. ft. of bench space. For larger plants with a well-developed canopy, the spray volume is approximately 3 quarts./100 sq. ft. of bench space. 


Drench applications of PAC O tend to be the most effective in reducing plant height and producing a uniform effect. Drench applications can be made, without phytotoxic effects, late in the growing cycle, at or near the point that marketable size is reached.

When applying PAC O by drench, it is important that:

  • Applications are made to moist potting media. 
  • Uniform distribution of drench is achieved.
  • No more than 10% run through of solution occurs.
  • Regard is paid to the growing media. Media containing bark or of high organic content may require the use of higher application rates.
  • When applied as a drench through sub-irrigation in saucers or benches etc. reduce rates by 25-50%.
  • When continuously applied through irrigation water reduce the rate used to 5-25% of a single conventional drench application.
  • Maximum application rates must never be exceeded.


Bulb soak applications of PAC O are extremely effective but rates and soaking times need to be adjusted according to species.


Applying PAC O by liner dip involves dipping the roots and media of seedling plugs or rooted cuttings in a treated solution prior to transplanting into the final container. Pre-transplant liner dip applications of PAC O can be effective in reducing the height of very vigorous plants that tend to grow rapidly, following transplant. Liner dip applications also allow the use of variable PAC O rates within single mixed-plant containers, thereby providing greater plant growth uniformity.

The moisture level of the media at the time of liner dip treatment will influence the degree of PAC O absorption, and thusly its availability to the roots. Under dry liner conditions, PAC O absorption will increase, therefore requiring a lower use rate. Media that is moist at the time of PAC O application will absorb less treated solution and will elicit a lesser treatment response.

General Recommendations 

Root Development: The degree of root development at the time of treatment can affect the plant’s response to PAC O. Poorly rooted or immature cuttings can be excessively stunted. Therefore, treat only well-rooted cuttings with liner dip applications of PAC O

Solution Depth: The depth of the treated solution may affect the activity level of a PAC O liner dip treatment. Since the majority of roots are located at the lower one-half of the plug, a solution depth covering at least 50% of the liner cell is recommended. 

Treatment Timing: The length of time from treatment to transplanting will have a minimal impact on PAC O activity, allowing for good flexibility. Times ranging between 2 hours to 10 days with liner dip treatments have been shown to provide equally effective results.

Use Rates: Due to the number of factors that can result in treatment variability; including soil moisture, light level, growing conditions, plant cultivar, root development and desired degree of growth control, optimum PAC O rates will vary. The key to ensuring consistency in results is to develop a practical system to standardize as many factors as possible, including media moisture level, duration of dip, the age of cuttings and length of time between treatment and transplant.

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