Paczol Ornamental Growth Regulator

Paczol Ornamental Growth Regulator

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Product Overview

Paczol Ornamental Growth Regulator is designed for use on ornamental plants grown in containers in greenhouses, nurseries, shadehouses, and interiorscapes. It is a highly active plant growth regulator that uses Paclobutrazol as its active ingredient to help reduce internode elongation for more desirable compact plants. It significantly cut down unwanted plant growth to achieve target height and produce more marketable plants. This unique formula has no phytotoxic effects when used as directed. Available in gallon size.

Features and Specs

Active Ingredient Paclobutrazol - 0.4%
For use in Ornamental plants grown in containers in nurseries, greenhouses, shadehouses, and interiorscapes.
Application Can be applied as a drench or spray, and maybe used through subirrigation, or as a bulb soak. The addition of wetting agents is not necessary.
Pet safe Yes, if used as directed on label.
Formulation Liquid.
Special Features Effectively reduces internode elongation, resulting in more desirable compact plants.
Shipping Weight 9.75 lbs
Manufacturer OHP Inc. (Mfg. Number: 986191)
EPA Registration 400-515-59807



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 persons, 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.


Be sure the sprayer is clean and not contaminated with any material. Fill the spray tank with half the required amount of water. Using the DILUTION TABLE (Table 1), determine the amount of PACZOL needed for the required concentration. Measure the desired volume accurately and add it to the tank. Fill tank with the remaining amount of required water. Agitate the mixture of PACZOL and water frequently to assure uniform distribution during application.

PPM Paczol Desired:

  • 1 - 0.032 fl. oz. per gallon / 1.0 ml/cc per gallon
  • 2 - 0.064 fl. oz. per gallon / 1.9 ml/cc per gallon
  • 3 - 0.096 fl. oz. per gallon / 2.8 ml/cc per gallon
  • 4 - 0.13 fl. oz. per gallon / 3.8 ml/cc per gallon
  • 5 - 0.16 fl. oz. per gallon / 4.7 ml/cc per gallon
  • 10 - 0.32 fl. oz. per gallon / 9.5 ml/cc per gallon
  • 20 - 0.64 fl. oz. per gallon / 19.0 ml/cc per gallon
  • 25 - 0.8 fl. oz. per gallon / 24.0 ml/cc per gallon
  • 30 - 1.0 fl. oz. per gallon / 28.0 ml/cc per gallon
  • 40 - 1.3 fl. oz. per gallon / 38.0 ml/cc per gallon
  • 50 - 1.6 fl. oz. per gallon / 47.0 ml/cc per gallon
  • 100 - 3.2 fl. oz. per gallon / 95.0 ml/cc per gallon
  • 200 - 6.4 fl. oz. per gallon / 190.0 ml/cc per gallon

* All PPM's on this label are expressed as active ingredient (a.i.).


Desired height control with PACZOL can be obtained with three different types of applications: sprays, drenches or bulb soaks.

Under certain conditions, sequential spray applications may be desirable.

Frequent agitation of the PACZOL solution and proper application techniques are critical in order to achieve desired results.

Be sure of your calculations, volume measurements and sprayer calibration. When in doubt, recalculate.


In spray applications, PACZOL penetrates into plant stems and is translocated to the terminal where it reduces internode elongation.

When applying a spray application, it is important that:

  • adequate spray volume is used to thoroughly wet plant stems. The misting technique used for some other growth regulators, where only upper leaves are covered with a light spray, will not produce desired results with PACZOL;
  • sprays are not applied to the point of excessive runoff into the potting media. The spray volume which drips down into the media may be desirable as it will be taken up by the roots and increase the effectiveness of PACZOL. However, too much runoff into the media may result in excessive height control;
  • the spray technique provides thorough, consistent, uniform coverage for all plants. Failure to do so may result in nonuniform height control.

PACZOL may be applied at any time of the day without danger of burning leaves or causing chlorosis.

Overhead irrigation or rain 30 minutes after spray applications does not reduce the effectiveness of PACZOL.

Addition of wetting agents for spray applications is not necessary.

The RECOMMENDED SPRAY VOLUME for small plants in small containers or plug trays which are closely spaced is 1-2 qts. / 100 sq. ft. of bench space.

For larger plants with a well developed canopy, a spray volume of 3 qts. / 100 sq. ft. of bench space is recommended.

Using SEQUENTIAL APPLICATIONS may provide more uniform growth regulation and safety against over-application. In general, sequential spray applications are to be applied using 50 - 100% of the lower recommended rate. Growers in cooler climates may have to use lower rates.

With some plant species, particularly chrysanthemums, hibiscus and azaleas, individual lateral shoots will outgrow the other laterals causing non-uniform plant appearance. This results when individual laterals do not receive enough chemical when spray is applied. The use of sequential applications will reduce this problem.


Application of PACZOL to the growing media will provide good control of plant height. PACZOL is readily absorbed by plant roots and translocated to the terminals.

Drench applications generally provide a longer lasting, more uniform height control than spray applications, having little effect on flower size. Drench applications are very useful when applied late in the production cycle when plants have reached, or are near, the desired marketing size. Late drench applications are particularly useful on poinsettias, chrysanthemums and bulb crops.

Drench applications should be made to moist potting media. This may be achieved by watering plants the day before treatments. Drench applications to dry media will result in poor distribution.

Multiple plants growing in the same pot require a more uniform distribution of drench solution to achieve uniform height control.

Drench Rates and Volumes: The rates recommended for soil drench applications are based on a drench volume of 4 fl. oz. of final solution for an average 6-inch ‘azalea’ pot. Based on this recommendation, one gallon of solution will treat 32 - 6-inch pots. For smaller or larger pots, a suitable drench volume is enough final solution applied to achieve total run through of no more than 10%, providing that the potting media is properly moist before treatment. Table 2 may be used as guide in determining appropriate drench volumes needed for the specified pot sizes. For the grower who likes to apply PACZOL as a known amount of active ingredient per pot, Table 2 also shows the amount of active ingredient found in a specific volume at a known concentration.

PACZOL can also be applied as a ‘drench’ through sub-irrigation in saucers, benches or flooded floors. Using this method, the solution is applied to the media through the bottom of the container. Because most plant roots grow in the lower half of the container, this sub-application of PACZOL delivers the chemical to the plant more efficiently than the typical drench application, and therefore requires the use of lower rates than the typical drench.

The optimum rates for a one-time sub-application is typically about 50-75% of the rate used in a typical drench. The optimum rate for continuous application in the irrigation water is about 10-33% of the rate needed for a one-time sub-irrigation application.


Soaking of bulbs in solutions of PACZOL is also a very effective way to attain height control. The rates used and length of soaking time will vary, depending on the species. (See the section on BULB CROPS for specific recommendations.)


This application method involves soaking plugs or root liners in a solution of PACZOL prior to transplanting into the final container. This is an alternate method of obtaining height control of vigorous growing plants, and is particularly useful on vigorous plug/liners being transplanted into mixed bowls.

In addition to cultural, varietal and environmental factors, the level of activity observed with pre-plant plug/liner soaks can vary depending on other factors such as:

Soak time: Plugs/liners that have been soaked long enough to be fully absorbed into the plug/liner media (30-120 secs.) will result in greater activity than those that have been quickly dipped in solution.

Extent of rooting: Well rooted plugs/liners will absorb more PACZOL and therefore result in more optimal activity than those that are unrooted or poorly rooted at the time application. Application to unroooted or poorly rooted plants can result in excessive stunting and negatively impact growth.

Media moisture level: Dry media will absorb more PACZOL than wet media and therefore results in greater activity.

Media should not be wet, but instead should be dry to moist (50% or less water holding capacity) at the time of application.



These factors may cause a variation in the amount of PACZOL needed to provide desired plant height.

Cultural practices may affect the plant's response to PACZOL. Plants which are grown at close spacing or in smaller pots and using high water and fertilizer levels may require an increase in the amount of PACZOL needed.

For drench applications, plants grown in media with pine bark or a high organic content may require higher rates of PACZOL than those grown in media without pine bark or with a low organic content.

Different varieties or cultivars within a given plant species may require a higher or lower rate of PACZOL. The taller, more vigorous varieties generally require more chemical than do the naturally short, less vigorous varieties. Growers should consult with plant and seed suppliers for vigor and other growth characteristics for newly released varieties.

Temperature can be the overriding factor in determining amount of PACZOL needed. Stem elongation increases with increased temperatures. Growers in warm climates need to use higher rates and/or more applications compared to those in cooler climates. The amount of PACZOL needed and number of applications may also vary depending on the time of year, with higher rates and/or more applications needed during warmer months.


Optimum PACZOL rates will vary with different growers and will depend on their individual desired final plant height, growing conditions, and application techniques. Different varieties or cultivars of the same species may respond differently to PACZOL.

Before PACZOL is applied to large numbers of plants, growers should conduct trials with small numbers of plants using the recommended rates to determine the optimum rates for their situations.

The rates recommended on this label are rate ranges and should be used only as guidelines. Do not exceed the maximum recommended rate.

The user should conduct trials on a small number of plants, adjusting the rate of PACZOL to achieve the desired height and length of control. For preplant bulb soak trials, it may be necessary to adjust both the rate and length of soak time in order to achieve desired results.

For plant species listed on the label, the user should run initial trials using the lowest recommended rates.


PACZOL is effective in controlling height of most ornamental crops.

Be sure to read and fully understand the section on DETERMINING OPTIMUM RATES before applying to large numbers of plants.


PACZOL can be used to control plant height, reduce bypass shoot elongation and promote flower bud initiation.

Spray applications are effective in the rate range of 100 to 200 PPM.

Drench applications are effective in the rate range of 5 to 15 PPM.

To control plant height and promote flower bud initiation, applications should begin when new growth, following final shaping, is 1 1/2 to 2 inches long.

To reduce bypass shoot development, applications should be made after bud set when bypass shoots are barely visible, or about 5 to 7 weeks prior to cooling.


Spray applications of PACZOL will provide height control of most bedding plants at a wide rate range of 5 to 90 PPM.

  • Do not use on fibrous begonias as they are very sensitive to PACZOL. Overly stunted plants can result if they receive spray drift from applications made to surrounding species.
  • Do not use on annual Vinca (periwinkle) as PACZOL may cause spotting of foliage, especially at high temperatures.

For bedding plants not specifically listed above, the user should determine optimum rates starting with a rate of 30 PPM in the Sunbelt Region and 15 PPM in the Northern Belt Region. Time of application should begin when new growth in height or width reaches 2 inches or when plants reach the desired size to hold them at a marketable stage.

Media sprays can be used to control the height of vigorous plugs, such as impatiens and salvia, that show excessive elongation soon after transplant. Rate recommendations for applications made just prior to transplant are in the range of 20 - 60 ppm, applied in a volume of 2 qts/100 sq. ft.

Late application timings and/or excessive rates may slow the growth of plants when transplanted. To avoid this, apply multiple applications at 1/4 - 1/2 the optimum rate.
High rates of PACZOL may delay flowering, especially of impatiens and petunia.

Drench applications are effective on bedding plants, but are recommended only for those plants in containers 6 inches or larger. The user should determine optimum rates, starting at 1 PPM.


Spray applications of PACZOL can also be used to effectively control height of bedding plant plugs. The recommended rate range of 1 to 20 PPM is much lower than the rate range for older bedding plants.

Media sprays can be used to control the height of vigorous plugs, such as marigold and snapdragon, that show excessive elongation soon after emergence. Rate recommendations for applications made at the time of, or within one week after seeding, are in the range of 5 - 30 ppm, applied in a volume of 2 qts./100 sq. ft.

Drench applications are not recommended for bedding plant plugs due to the sensitivity and extremely low rates needed.

For all uses of PACZOL on plugs, determining optimum rates should include an evaluation of the crop performance after transplanting to insure that treatment does not excessively reduce growth during the finishing stage or in the landscape.


Height control can be achieved on a variety of bulb crops by any of the three application types.

Spray applications, although moderately effective, are the least desirable method for controlling height. Sequential applications are recommended in order to achieve desired uniformity. Applications should begin when plants are 2 to 4 inches tall.

Drench applications are very effective in the rate range of 8 to 160 PPM. Optimum rates vary widely, depending on species. Timing of application will also vary, depending on species. For bulbs which require a cold period, PACZOL is generally applied 1 to 5 days after removal from the cooler. For most other bulb types, application should be made when newly emerged shoots are 1 to 2 inches tall.

Preplant bulb soaks are also very effective. Effective rates for most species are in the range of 5 to 25 PPM, with a soaking time of 5 - 15 minutes. In general, lower use rates will require longer soaking times.


PACZOL is effective in controlling height of pot chrysanthemums when applied as either a spray or drench.

Spray Applications are effective at rates of 50 to 200 PPM. Applications should begin when axillary shoots are 2 to 3 inches long. PACZOL can be applied earlier to vigorous varieties if additional control is desired.

Sequential applications of lower rates generally provide more uniformly shaped plants than single spray applications.

Drench applications of PACZOL are effective at recommended rates of 1 to 4 PPM. Application timing during early production is when axillary shoots are 2 to 3 inches long.

Seasonably late applications are sometimes required at the time of disbud to prevent late stretch. Unlike spray applications, the drench can be safely applied with little to no effect on flowering.

Because pot chrysanthemums are usually planted with multiple cuttings per pot, uniform application is critical to achieving desired results.

F. FLOWERING PLANTS / FOLIAGE PLANTS (not specifically listed)

PACZOL is effective as a spray or drench application in controlling height on a wide variety of other flowering plants and foliage plants. It can be used as either a holding agent to stop growth (e.g., interiorscape) or a toning agent to slow growth (e.g. when pot crops or hanging baskets are at or near marketable size). In general, herbaceous species will require lower rates than woody species. Trials should be conducted using rates outlined in the section on DETERMINING OPTIMUM RATES.


Geraniums are particularly sensitive to PACZOL. The user must determine optimum rates before applying to large numbers of plants.

Spray applications of PACZOL at recommended rates of 10 to 30 PPM will effectively control growth of geraniums. Early applications may require lower rates to avoid overstunting. Time of application for zonal geraniums is when growth is 1 1/2 to 2 inches long; for seed geraniums, 2 to 4 weeks after transplanting or when needed.

PACZOL will reduce late stretch when applied as the flower stems begin to elongate.

Drench applications, although effective, should be made with caution due to the extreme sensitivity of geraniums to PACZOL. Trials should be conducted to determine optimum rates.


Spray applications of PACZOL at 30 to 150 PPM will effectively reduce shoot elongation. Application should be made when laterals are 1 to 4 inches long, depending on desired final plant size. Single applications control lateral growth for 3 to 6 weeks. Sequential applications may provide more uniform plant shape.

PACZOL can be applied 1 to 2 weeks prior to flowering to prevent late stretch.

Drench applications will also effectively reduce shoot elongation. Trials should be conducted using recommended rates outlined in the section on DETERMINING OPTIMUM RATES.


Perennial plants make up a wide variety of plant forms, many of which grow very tall. Others, which may have naturally low growing foliage, will develop flowers on tall spikes which, when in flower, may be difficult to ship or display. The use of PACZOL to control height of large, unruly perennial species has become an effective strategy to increase their attractiveness and marketability.

Spray applications of PACZOL are effective on a wide variety of perennial plants in the rate range of 30 - 200 ppm.

Drench applications are effective in the 1 - 30 ppm range, and are useful to hold or tone plants when they are at or near a marketable size.


Spray Applications of PACZOL will effectively control height of poinsettias. Recommended rates are 10 to 30 PPM for most areas of the U.S. In southern Florida, higher rates of 15 to 45 PPM are recommended.

Single applications may be made using the higher recommended rates. However, sequential applications initially using lower rates will provide better safety against overly retarded plants. For the subsequent applications use 50 to 100% of the initial rate, depending on plant vigor at the time of reapplication.

Applications to slower growing varieties in cool climates should begin when axillary shoots are 2 to 3 inches long. For vigorous growing varieties in warm climates, applications should begin when axillary shoots are 1 1/2 to 3 inches long. Sequential applications may be applied 1 to 3 times, at 7 to 14-day intervals, depending on plant vigor/growth.
Seasonably late applications of PACZOL will reduce plant height, but, like most PGR's, may also reduce bract size. To prevent this, PACZOL should not be applied after initiation of short days. As a guide, do not apply PACZOL sprays after October 1 for areas outside of Florida, or after October 25 in Florida.

Drench applications are also an effective means of height control, and are most commonly used for late season application to plants which have initiated bracts or have reached or are near their desired marketing size. Recommended rates are in the range of 0.25 to 3 PPM, based on drench volume of 4 fl. oz. / 6- inch pot.

Application during early production should be made when axillary shoots are 1 1/2 to 2 inches long. Seasonably late applications are sometimes required after initiation of short days to prevent late stretch and, unlike spray applications, can be safely applied with little to no effect on bract size.

NOTE: Optimum PACZOL rates and timings for both spray and drench applications to poinsettias will vary depending on the variety.


PACZOL is effective in controlling height and initiating flower bud formation on a wide variety of woody plants using both spray or drench applications.

Rate ranges for different species vary greatly. Trials should be conducted using rates outlined in the section on DETERMINING OPTIMUM RATES.

Examples of woody plants on which the product can be applied are:

Azalea, Bougainvillea, Camellia, Cotoneaster, Euonymus, Hibiscus, Hyrangea, Ilex (Holly), Juniper, Kalmia, Ligustrum, Magnolia, Photinia, Pine, Rhododendron, Rose.


Do not apply directly to water, to areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment washwaters.

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