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Publication #PI-102

Plant Growth Regulators1

Frederick M. Fishel2

This publication provides the meaning and definition of the term, "plant growth regulator," addresses patterns of use for plant growth regulators, and provides a listing of plant growth regulators registered for use in Florida.

What are plant growth regulators?

Simply put, plant growth regulators (also known as growth regulators or plant hormones) are chemicals used to alter the growth of a plant or plant part. Hormones are substances naturally produced by plants, substances that control normal plant functions, such as root growth, fruit set and drop, growth and other development processes. Plant growth regulators are regulated as pesticides by the Florida Department of Agriculture and Consumer Services (FDACS) and must be registered with the FDACS for lawful use in Florida like any pesticide lawfully used in Florida.

FDACS Definition of "Plant Regulator"

Any substance or mixture of substances intended, through physiological action, for accelerating or retarding the rate of growth or maturation or for otherwise altering the behavior of ornamental or crop plants or the produce thereof, but not including substances intended as plant nutrients, trace elements, nutritional chemicals, plant inoculants, or soil amendments.

History and Use of Plant Growth Regulators

The use of plant growth regulators in agricultural production within the United States began in the 1930s. The first discovery and use of plant growth regulators was with acetylene and ethylene, which enhanced flower production in pineapple. Subsequently, use of plant growth regulators has grown exponentially to become a major component of agricultural commodity production.

Certain herbicides and insecticides that are not true plant growth regulators cause some plant-growth-regulating effects. For example, the widely used insecticide carbaryl is used to thin apple fruit from trees and to aid in encouraging annual bearing.

According to the American Society for Horticultural Science, plant growth regulators fall into six major classes. Table 1, below, lists these classes with the plant development function(s) that are controlled by the plant growth regulators. Table 1 also provides examples of the practical uses with which plant growth regulators are typically associated.

Table 2 provides Florida-specific information on plant growth regulators registered by the FDACS. This table also includes major commodities in the United States that are associated with plant growth regulators and the primary function(s) of plant growth regulators and includes examples of trade names for plant growth regulators registered for use in Florida.

Additional Information

American Society for Horticultural Science: http://www.ashs.org/

Tables

Table 1. 

Plant growth regulator class, associated function(s) and practical uses.

Class

Function(s)

Practical uses

Auxins

Shoot elongation

Thin tree fruit, increase rooting and flower formation

Gibberellins

Stimulate cell division and elongation

Increase stalk length, increase flower and fruit size

Cytokinins

Stimulate cell division

Prolong storage life of flowers and vegetables and stimulate bud initiation and root growth

Ethylene generators

Ripening

Induce uniform ripening in fruit and vegetables

Growth inhibitors

Stops growth

Promote flower production by shortening internodes

Growth retardants

Slows growth

Retard tobacco sucker growth

Table 2. 

Plant Growth Regulators Registered for Use in Florida.

Active ingredient

Registered crops and functions

Trade names®*

Ancymidol

Ornamental plants – growth inhibitor

Abide, A-Rest

Butralin

Tobacco – shoot inhibitor

Butralin

Alcohols

Tobacco – shoot inhibitor

Fair, Royaltac M, Sucker-Plucker, Off-Shoot, Contact-85

Chlormequat chloride

Ornamental flowers – shoot inhibitor

Citadel, Cycocel, E-Pro

Cytokinin#

Ornamental plants, vegetables, fruits including citrus – hasten maturity, enhance fruit color, growth enhancer, enhance tuber color, improve tuber quality

Conklin, Culbac, Cytoplex, Early Harvest, Foli-Zyme, Goldengro, Happygro, Incite, Megagro, Ascend, Radiate, Stimulate, Suppress, Validate, X-Cyte

Daminozide

Ornamental plants – growth inhibitor

B-Nine, Compress, Dazide

Ethephon

Turfgrass – reduces mowing frequency

Various fruits, vegetables, and nuts – hastens ripening and maturity, enhance fruit color and floral stimulant

Cucurbits – increases flowering

Ground covers – inhibits flowering

Ornamental trees – inhibits fruiting

Tobacco and cotton – hastens maturity

Cereal grains and grasses grown for seed – reduces lodging

Boll Buster, BollD, Cerone, Cotton Quik, Ethrel, Finish, Flash, Florel, Mature, MFX, Prep, Proxy, Quali-Pro, SA-50, Setup, Super Boll, Whiteout

Ethylene

Fruits and tobacco – enhance fruit color, hasten ripening

Agronomic row crops – soil treatment for witchweed control

Banana Gas, Nature-Ripe

Flurprimidol

Ornamental woody plants and ground covers – reduces pruning

Turfgrass – reduces mowing frequentcy

Cutless, Legacy, Mastiff, Topflor

Gibberellic acid#

Small fruits, cucurbits – increase fruit set

Citrus – promote rind/peel integrity, prevent fruit drop

Rice, cotton – growth enhancer

Ascend, Cytoplex, Early Harvest, Falgro, Florgib, Foli-Zyme, GA3, GibGro, Green Sol, Incite, N-Large, PGR IV, Pro-Gibb, Release, Rouse, Ryzup, Stimulate

Gibberellin mixtures

Cut flowers – plant preservative

Tree fruit – increase fruit size, hasten maturity, shoot stimulant

Evergreen trees – floral stimulant, stimulate germination

BVB, Chrysal, Fascination, Procone

Indole-3-butyric acid (IBA)#

Ornamental plants and trees – root stimulant

Numerous trade products

Maleic hydrazide, potassium salt

Tobacco – shoot inhibitor

Stored bulbs – sprout inhibitor

Fair, Rite-Hite, Royal, Sucker Stuff,

Mefluidide

Ground covers, shrubs, ornamental trees – reduces pruning

Turfgrass – reduces mowing frequency

Embark, Sta-Lo

Mepiquat chloride

Cotton - growth inhibitor, enhance uniform fruit maturity

Pix

Mepiquat pentaborate

Cotton – growth inhibitor, enhance uniform fruit maturity

Pentia

Naphthalene-acetic acid (NAA)#

Ornamental plants – stimulates rooting, increase vegetative growth

DipN Grow, Goldengro, Hi-Yield

1-Naphthaleneacetamide (NAD)

Woody ornamental cuttings – rooting stimulant

Rootone

n-Decanol

Tobacco – shoot inhibitor

Antac, FST-7, Royaltac

Paclobutrazol

Ornamental flowers – promotes uniform flowering

Ornamental plants – reduces internodal length

Ornamental trees – growth inhibitor

Turfgrass – increased plant thickness, growth inhibitor

Bonzi, Cambistat, Cutdown, Downsize, Florazol, Paclo, Paczol, Piccolo, Profile, Shortstop, Trimmit, Turf Enhancer

Prohexadione calcium

Peanut, Tree fruit, turfgrass grown for seed – growth inhibitor, reduce vegetative growth

Apogee

Trinexapac-ethyl

Turfgrass – reduces mowing frequency

Armor Tech, Goldwing, Governor, Groom, Legacy#, Primeraone, Primo, Provair, Solace, T-Nex, T-Pac

Uniconazole

Ornamental plants – growth inhibitor

Concise, Sumagic

*Consult individual labels for specific sites and commodities approved for use.

#At least one active ingredient component of product.

Footnotes

1.

This document is PI-102, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date February 2006. Revised April 2009. Reviewed June 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Frederick M. Fishel, associate professor, Agronomy Department, and director, Pesticide Information Office, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.