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Plant growth regulators (PGRs) for slowing top-growth and reducing the trimming of shrubs, trees and woody-type groundcovers came onto the market around 20 years ago. Their acceptance and use was greatest among large, multi-market landscape contractors with research specialists and training teams. However, in recent years, ornamental PGRs appear to have become increasingly used by shrubbery maintenance professionals as well.
In Virginia Beach, Va., the 700-resident Atlantic Shores Retirement Community has used an ornamental PGR since 2004, according to David Myers, grounds supervisor of the 70-acre property. ?EUR??,,????'?????< The crew at Atlantic Shores usually performs their first trim in May after the ligustrum has flushed out. ?EUR??,,????'?????< Also, using the PGR has enabled him to keep the height of his ligustrum hedges below six feet, thus allowing them to be trimmed without ladders. Other ornamental applications that have been made with the PGR have included a two oz. rate applied to cleyera japonica, burford holly and fosteri holly. Also, a 200 feet long fosteri hedge, sprayed end-to-end produced little or no growth for 60 days with only a minimal amount of trimming. Pittosporum (variegated) treated at the one oz. rate was held in check and did very well all summer, Myers noted.
The crew at Atlantic Shores usually performs their first trim in May after the ligustrum has flushed out. ?EUR??,,????'?????<
Also, using the PGR has enabled him to keep the height of his ligustrum hedges below six feet, thus allowing them to be trimmed without ladders.
Other ornamental applications that have been made with the PGR have included a two oz. rate applied to cleyera japonica, burford holly and fosteri holly. Also, a 200 feet long fosteri hedge, sprayed end-to-end produced little or no growth for 60 days with only a minimal amount of trimming.
Pittosporum (variegated) treated at the one oz. rate was held in check and did very well all summer, Myers noted.
In Greensboro, N.C., New Garden Landscape & Nursery employs 215 employees in its two retail stores, ornamental nursery, and landscape maintenance operations, which includes design, build, and irrigation services.
Dean Gardiner joined the firm four years ago and introduced a PGR into their spray program. As manager of insect and disease services, Gardiner explained, ?EUR??,,????'?????<
Then last year, New Garden checked out a granular PGR. ?EUR??,,????'?????< To Gardiner, the most appealing thing about the granular PGR was it could be applied by minimally trained workers, even on rainy days when mowers could not be operated. He spent a day the last week of April last year training four workers to spread the granules using Spred-Rite G granule applicators.
To Gardiner, the most appealing thing about the granular PGR was it could be applied by minimally trained workers, even on rainy days when mowers could not be operated. He spent a day the last week of April last year training four workers to spread the granules using Spred-Rite G granule applicators.
One of the training day sites was Astor Point, an older upscale townhouse community of some 120 residences, mostly duplexes. Three weeks after the granules were applied, the account executive responsible for the property told Gardiner he was concerned that the shrubbery growth didn?EUR??,,????'?????< Gardiner had tested high, low and mid-range dosages in a couple instances where plant groupings at Astor Point were such that they could be divided and treated for such comparisons. Originally, he had envisioned ground-applied granules as an advantage in treating trees, which can require a ladder or aerial lift to trim. But then he learned the granule marketer hadn?EUR??,,????'?????< Between March and October, spraying shrubs with PGRs frees up a half day of labor per week, and up to a full day per week during periods of fastest growth in mid-summer for Livengood?EUR??,,????'?????< The granules were experimentally applied at the regular shrubbery rates, plus double and triple rates out to the dripline of fosteri holly trees about 25 ft. tall. A similar set of comparisons was done with nelly stevens hollies almost as tall at a country club, along with some large fosteri trees there, too. ?EUR??,,????'?????< A dwarf burford hedge at the country club was treated with the granular PGR but Gardiner got there a week too late to see how it shaped up. About seven weeks after treatment a New Garden landscape crew stopped by for other work and seeing inadequately controlled shoots, they pruned the hedge. The grounds crew at the Chattanooga Choo Choo Holiday Inn cares for over 800 roses in three dozen beds. They are bordered with dwarf yaupon hedges, which used to demand almost continual shearing, but only about a third as much since they began spraying with PGR after trimming. Choo Choo Gardens Lori Martinez heads a five-person grounds crew for a nationally renowned ornamental garden in Chattanooga, Tenn. She says she always welcomes the first flush of new growth on her dwarf yaupon holly hedges as they rebound in the spring, usually around the last week of April. By late summer, though, shearing the seemingly endless miles of hedges at the Chattanooga Choo Choo gardens used to have her and her staff exhausted?EUR??,,????'?????< Bottom line, between March and November, using PGRs reduces shearing and frees up time for you and your crew. With a half day per week, and up to a full day per week during the heaviest growth periods in the summer, there is no doubt you will be able to spend less of your man-hours on trimming shrubs and instead on more pressing matters around the grounds.
Gardiner had tested high, low and mid-range dosages in a couple instances where plant groupings at Astor Point were such that they could be divided and treated for such comparisons. Originally, he had envisioned ground-applied granules as an advantage in treating trees, which can require a ladder or aerial lift to trim. But then he learned the granule marketer hadn?EUR??,,????'?????<
The granules were experimentally applied at the regular shrubbery rates, plus double and triple rates out to the dripline of fosteri holly trees about 25 ft. tall. A similar set of comparisons was done with nelly stevens hollies almost as tall at a country club, along with some large fosteri trees there, too. ?EUR??,,????'?????< A dwarf burford hedge at the country club was treated with the granular PGR but Gardiner got there a week too late to see how it shaped up. About seven weeks after treatment a New Garden landscape crew stopped by for other work and seeing inadequately controlled shoots, they pruned the hedge.
A dwarf burford hedge at the country club was treated with the granular PGR but Gardiner got there a week too late to see how it shaped up. About seven weeks after treatment a New Garden landscape crew stopped by for other work and seeing inadequately controlled shoots, they pruned the hedge.
Lori Martinez heads a five-person grounds crew for a nationally renowned ornamental garden in Chattanooga, Tenn. She says she always welcomes the first flush of new growth on her dwarf yaupon holly hedges as they rebound in the spring, usually around the last week of April. By late summer, though, shearing the seemingly endless miles of hedges at the Chattanooga Choo Choo gardens used to have her and her staff exhausted?EUR??,,????'?????< Bottom line, between March and November, using PGRs reduces shearing and frees up time for you and your crew. With a half day per week, and up to a full day per week during the heaviest growth periods in the summer, there is no doubt you will be able to spend less of your man-hours on trimming shrubs and instead on more pressing matters around the grounds.
Bottom line, between March and November, using PGRs reduces shearing and frees up time for you and your crew. With a half day per week, and up to a full day per week during the heaviest growth periods in the summer, there is no doubt you will be able to spend less of your man-hours on trimming shrubs and instead on more pressing matters around the grounds.
Francisco Uviña, University of New Mexico
Hardscape Oasis in Litchfield Park
Ash Nochian, Ph.D. Landscape Architect
November 12th, 2025
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