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.

PLANT GROWTH REGULATORS FOR TURF

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.

PGRS FOR LANDSCAPE ORNAMENTALS*

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.

PGR SOURCES¹

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.

CONTACT INFORMATION

Andersons — (419) 893-5050 — www.andersonsgolfproducts.com
Aventis — (800) 843-1702 — www.aventischipco.com
LESCO — (800) 321-5325 — www.lesco.com
Micro Flo — (800) 451-8461 — www.microflocompany.com
Monterey — (559) 499-2100 — www.montereychemical.com
Opti-Gro — (800) 527-9919 — www.opti-gro.com
PBI/Gordon — (800) 821-7925 — www.trimec.com
SePRO — (800) 419-7779 — www.sepro.com
Syngenta — (800) 395-TURF — www.syngentaprofessionalproducts.com
Top Pro — (800) 888-5948 — www.topprospecialties.com
Tree Tech — (352-528-5335 — www.treetech.net
Uniroyal — (203) 573-2028 — www.cromptoncorp.com
Valent Biosciences — (800) 323-9597 — www.valentbiosciences.com