CHEMICAL UPDATE: Plant growth regulators

Plant growth regulators, or PGRs, offer various benefits. Turf and landscape managers typically think of them as tools to reduce plant growth, but this is just one of their attributes. Innovative professionals are using PGRs both to reduce maintenance and to improve plant vigor.

Turf uses

PGRs definitely can reduce mowing requirements. However, they do much more. For example:

  • PGRs suppress turf growth during overseeding to give young seedlings a quick start.

  • Some PGRs inhibit or suppress unsightly Poa annua seedheads.

  • PGRs eliminate tall seedheads in some roadside grasses (which, in some cases, might be the only reason to mow).

  • PGRs can differentially suppress growth of various turfgrass species, giving the desirable turfgrass a competitive advantage over Poa annua.

  • “Chemical edging” with PGRs controls growth of turf around tree trunks, landscape fixtures and edges, which can significantly reduce labor needed for trimming.

  • Some PGRs can improve the overall health and vigor of their turf, resulting in better color, improved stress tolerance and perhaps better root development.

Active ingredient Turfgrass registrations1 Uses Uptake Main effect/mode of action3
Bermudagrass Zoysiagrass St. Augustinegrass Kentucky bluegrass Tall fescue Creeping bentgrass Fine fescues Perennial ryegrass Kikuyugrass Bahiagrass Centipedegrass Poa annua Overseeding registration2 Registration for close-cut greens Root absorbed Foliar absorbed
Ethephon (Proxy) X X X X X X Growth/seedhead inhibition
Flurprimidol X X X X X X X X Growth/seedhead inhibition
Gibberellic acid X X Color retention
Indolebutyric acid + gibberellic acid X X X X X X X X X X X X Improve root growth, vigor
Maleic hydrazide X X X X X X X X Growth/seedhead inhibition
Mefluidide X X X X X X X X X X X X Growth/seedhead inhibition
Mefluidide + imazethapyr + imazapyr X X X X X Growth/seedhead inhibition
Methyl chlorflurenol X X X X X X Growth/seedhead inhibition
Paclobutrazol X X X X X X X X X X GA inhibitor
Trinexapac ethyl X X X X X X X X X X X X X GA inhibitor
1 Labels may not allow all uses on all turfgrasses indicated. Check product labels for specific use instructions.
2 This table indicates which products' labels specify overseeding use. Others may not specify this use but do not forbid it either, and so may be appropriate for this use.
3 See “Classifying PGRs” on previous page.

Ornamental uses

Ornamental PGRs provide some benefits comparable to those of turf PGRs, but also others unique to ornamentals:

  • PGRs reduce trimming needs for trees and shrubs.

  • PGRs allow grounds care professionals to eliminate messy or dangerous fruit from trees.

  • PGRs also suppress sucker and sprout growth.

  • Certain ornamental PGRs can even improve root development, branching and overall vigor.

Are PGRs right for you?

To successfully integrate PGRs into your maintenance program, it's important to carefully balance the cost of the application with the anticipated savings in maintenance. PGRs may not always be an economical choice, but they often are.

Using PGRs to improve plant appearance or health, or improve establishment during overseeding, can be difficult to quantify in dollars and cents, and can be more of a judgment call based on agronomic and aesthetic considerations. By contrast, an application that reduces trimming (of a long hedge, to use one example) may be a clear-cut labor-saver.

The following tables are a general guide to PGRs available for turf and landscape ornamental use. Use them for preliminary planning only. They are not a substitute for label instructions, which you must read and follow whenever you use a PGR, as with any pesticide.

Active ingredient Primary use(s)
Dikegulac-sodium Reduces growth of trees, shrubs and groundcovers; reduces flowering and fruit on olive, privet, Japanese holly and multiflora rose.
Ethephon (Florel) Eliminates fruit on olive, crabapple and carob trees; removes mistletoe from coniferous and deciduous trees.
Indole-3-butyric acid (auxin) Microinjection for flower/fruit elimination on sweetgum
Indolebutyric acid + gibberellic acid Promotes root growth and vigor of trees and shrubs.
Maleic hydrazide Reduces growth of trees and shrubs.
Mefluidide Reduces growth of trees, shrubs, ground covers and herbaceous ornamentals.
Methyl chlorflurenol Eliminates fruit set, reduces plant growth.
Naphthalene acetic acid (NAA) Prevents root suckering and trunk and basal sprouts in wood ornamentals.
* Does not include PGRs registered only for greenhouse/nursery use.

Active ingredient Brand (manufacturer)
Dikegulac-sodium Atrimmec (PBI/Gordon)
Ethephon Ethephon 2 (Top Pro)
Florel (Monterey)
Pistill (Monterey)
Proxy (Chipco/Aventis)
Flurprimidol Cutless (SePRO)
Gibberellic acid RyzUp (Valent Biosciences)
Indolebutyric acid + gibberellic acid PGR IV (Micro Flo)
Indole-3-butyric acid Snipper (Tree Tech)
Maleic hydrazide Royal Slo-Gro (Uniroyal)
Mefluidide Embark T&O, Embark 2S (PBI/Gordon)
Sta-Lo (Opti-Gro)
Mefluidide + imazethapyr + imazapyr Stronghold (PBI/Gordon)
Methyl chlorflurenol Maintain CF 125 (PBI/Gordon)
Naphthalene acetic acid (NAA) Sucker Stopper Concentrate/RTU (Monterey) Tre-Hold (Amvac)
Paclobutrazol TGR (Andersons)2
Trimmit (Syngenta)
Trinexapac ethyl Primo (Syngenta)
Triple Play (LESCO)3
1 No endorsement is implied by this listing, nor is criticism implied by omission.
2 Available in combination with granular fertilizers, as well as singly as a liquid.
3 Combination with chelated iron + fertilizer.


Andersons — (419) 893-5050 —
Aventis — (800) 843-1702 —
LESCO — (800) 321-5325 —
Micro Flo — (800) 451-8461 —
Monterey — (559) 499-2100 —
Opti-Gro — (800) 527-9919 —
PBI/Gordon — (800) 821-7925 —
SePRO — (800) 419-7779 —
Syngenta — (800) 395-TURF —
Top Pro — (800) 888-5948 —
Tree Tech — (352-528-5335 —
Uniroyal — (203) 573-2028 —
Valent Biosciences — (800) 323-9597 —

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