Topflor effectively reduces internode elongation through the inhibition of gibberellic acid
(GA) biosynthesis, resulting in a more desirable plant. The active ingredient in Topflor,
flurprimidol, is a nitrogen-containing heterocycle compound of the pyrimidine chemical
class. Flurprimidol acts as an inhibitor of enzymes catalyzing the steps in the GA
biosynthetic pathway that involve oxidation of ent-kaurene to ent-kaurenoic acid, a GA
Topflor has been shown to increase the quality of plants, even in the absence of growth
reduction. Some of these desirable qualities include enhanced leaf and bloom color, higher
chlorophyll content, greater leaf thickness, stronger stems, and decreased water loss.
Topflor is a 0.38% formulation containing 14.4 grams of flurprimidol per gallon of product.
Topflor has a Caution label with a low 12-hour re-entry interval (REI). Required personal
protective equipment (PPE) includes: coveralls, chemical-resistant gloves made of any
waterproof material, long sleeved shirt and pants, and shoes plus socks.
Factors that influence Topflor efficacy
Cultivars or varieties within a given plant species may respond differently to Topflor.
Varieties that are taller or more vigorous generally require more Topflor than naturally
short or less vigorous varieties. Stage of plant growth at the time of application will
also influence the amount of Topflor needed.
Environmental conditions can also strongly influence the response to Topflor and,
therefore, the amount of product applied. Growers in warm climates may need to use higher
rates and/or more applications compared to those in cooler climates. The Topflor rate, as
well as number of applications, may also vary depending on the time of year, with higher
rates and/or more applications needed during warmer months.
Cultural practices may affect the plant's response to Topflor. Plants that are
grown at close spacing or in small pots and using high water and fertility levels may
require higher rates of Topflor to achieve the desired response. The effectiveness of a
Topflor drench may be reduced in root media that utilizes a high amount of pine bark.
Another factor that influences the amount of Topflor required for an optimum growth
response is application method (spray or drench) and technique including the uniformity
of coverage and degree to which the spray solution is allowed to run off the pot.
Topflor has been found to have acceptable plant tolerance in research trials for those
crops tested and listed within this guide. However, due to the large number of species,
varieties and cultivars and variable growing conditions, it is impossible to test every
plant and variety or cultivar for tolerance to Topflor. SePRO has not determined whether
Topflor can be used safely on all ornamental plants.
Establish specific application rates based on small-scale treatments under actual use
conditions. Determine and keep records as to plant species and cultivar sensitivity before
applying Topflor to a large number of plants.
Topflor Application Methods
Plants absorb Topflor through foliage, stems, and roots. Topflor may be applied as a
spray, drench or chemigation to achieve the desired plant height control. Use industry
standard application equipment, which may include backpack sprayers, low-pressure hand wand
drench applicators, or other similar equipment. Additionally, standard chemigation
equipment and practices may also be used. Multiple or split applications may allow greater
treatment flexibility, more uniform growth regulation, and safety from over-application and
may be, therefore, desirable.
How to Mix Topflor
The sprayer must be clean and not contaminated with other chemicals. Use the Dilution
Table (Table 1) to determine the amount of Topflor and water needed for the required
concentration. Fill the spray tank with half the required amount of water. Measure the
desired Topflor volume accurately and add it to the tank. Fill tank with the remaining
amount of required water. Agitate the Topflor and water mixture frequently to assure
uniform distribution during application.
Table 1: Dilution Table
|PPM Topflor desired concentration
||mL per gallon solution
||fl. oz. per gallon solution
||fl. oz. per 10 gallon solution
||fl. oz. per 100 gallon solution
Topflor applied as a foliar spray is absorbed through plant foliage and stems.
Additional growth regulation will result from root uptake of Topflor reaching
the root medium as runoff from foliar treatments or over-spray.
Dilute Topflor to the desired concentration using Table 1.
When applying as a spray, the following should be noted:
Do not use additional wetting agents in combination with Topflor as crop injury may occur.
The spray technique used should provide consistent and uniform coverage over all treated plants. Uneven application or over-application may result in irregular or excessive growth control.
Adequate spray volume should be used to thoroughly wet the plant foliage. The spray volume that drips down to the
stem or media may be desirable as it will be taken up by the both the stems and roots increasing the effectiveness
of Topflor. However, too much runoff into the media may result in excessive height control.
Apply uniformly at a rate of 1 gallon of spray per 200 sq. ft. of growing area, regardless of plant spacing. For
small plants in small containers or plug trays that are closely spaced, use 0.5-1 gallon of spray per 200 sq. ft. of
growing area. For larger plants with a well-developed canopy, a spray volume of 1.5 gallons per 200 sq. ft. of growing
area is recommended.
Typical foliar application rate is 0.5 ppm to 80 ppm (varies by cultivar), with a maximum of 200 ppm, applied in 1
gallon of spray mix over 200 square feet.
Do not allow spray drift to contact non-target plants.
Topflor applied as a drench provides treatment accuracy for consistently uniform results.
Topflor is readily absorbed by the roots and translocated to the terminals. Root medium
should be moist, but not wet at the time of treatment. Best results are obtained when
moisture content allows the drench treatment to become well distributed and retained
entirely within the pot. This may be achieved by watering the plants the day before
treating. Response may be variable if part of the drench solution is lost to flow-through
or if root medium is too dry to allow for even distribution of the treatment, especially
when multiple cuttings are in the same container. Generally, a volume of 2 fl. oz. (59 ml)
is required to treat a 4-inch pot or 4 fl. oz. (118 ml) for treatment of a 6-inch pot
(Table 2). Typical application rate is 1 gallon of drench solution per 32 six inch potted
plants. Dilute Topflor to the required concentration using the method described in Table 1.
When applying as a drench, the use of pine bark in root media may reduce the effectiveness
of drench treatments.
Table 2: Drench Volume Application Guidelines
NOTE: The recommended drench volumes were based on the soil capacity of a common 6-inch
"azalea-type" pot. Extrapolating the recommendation for this type pot to smaller or larger
containers may not be correct for the total drench volume, but should only be used as a
guideline. The user must determine the appropriate rate and drench volume needed to
achieve the desired result, based on both pot size and root medium used.
|Pot Diameter (Inches)
||mg a.i. Topflor/pot from solutions mixed at the following ppm*