Plant growth regulators (PGRs) are familiar tools to many growers, though their use varies widely. While some growers regularly incorporate PGRs into their operations, others avoid them for reasons that may no longer hold true. To clarify some of these misconceptions, we spoke with industry experts Dudley Dabbs, Sales Manager at Fine Americas, and Dr. JC Chong, Ornamental Technical Development Manager at SePRO, who shared their insights on the subject.
PGRs Are Too Expensive
A common belief among some growers is that PGRs are too costly to justify their use. However, both Dabbs and Chong argue that PGRs can actually save money in the long run. While they do represent an investment, the benefits in labor savings, improved plant marketability, and better scheduling flexibility can make them a worthwhile choice.
“Large and medium-sized growers have realized that PGRs aren’t an added expense—they’re a tool that makes them money,” says Dabbs. “Labor is expensive, and finding skilled workers is harder than ever. While smaller operations may try to replace PGRs with additional labor, the costs of moving plants and controlling their growth can quickly add up.”
Dabbs explains that weather conditions, such as extended cloudy periods, can cause plants to stretch, requiring extra labor to reposition them. “A PGR keeps the plants in check, reduces the need for frequent moving, and controls plant height,” he says.
Chong also highlights the labor-saving benefits, particularly in woody perennial production. Instead of pruning plants repeatedly, PGRs allow growers to prune once and then use the regulator to maintain the desired shape throughout the growing cycle.
PGRs Are Not Effective on All Plants
Another misconception is that PGRs are only suitable for certain plant types. However, experts agree that PGRs are widely applicable and effective across various plant categories, including annuals, herbaceous perennials, and woody plants.
Chong notes that PGRs are commonly used in landscape applications, such as tree and shrub control, and that many growers are beginning to explore their potential in nursery production for woody plants. Dabbs emphasizes that the range of crops that PGRs can be used on is extensive. “You’ll find detailed lists on the product labels showing a wide variety of crops that benefit from PGR use,” he says.
However, Dabbs and Chong both point out that different crops may require different application rates. “It’s important to adjust PGR doses based on the specific plant species,” Chong advises. For growers managing a variety of crops, grouping plants by similar growth patterns or application needs can simplify the process.
PGRs Delay Flowering
Some growers worry that using PGRs will delay flowering or harm the size of the flowers. While it’s true that misapplication of certain PGRs can result in stunted blooms or delayed flowering, these issues are typically caused by incorrect dosage or application timing.
Chong explains that one of the main concerns with PGRs is the potential for overdosing, which can cause phytotoxicity, a condition that affects plant health. “Overapplying PGRs is the main reason for problems like delayed flowering,” he says. Dabbs agrees, advising growers to carefully experiment with application rates to avoid adverse effects.
However, the risk of delaying flowering can be mitigated by choosing the right PGR and applying it correctly. Dabbs recommends using paclobutrazol, one of the most popular PGRs, as a drench rather than a spray if flowering timing is a concern. “This method is not only more economical but also provides longer-lasting control without affecting flower timing,” he says.
PGRs Must Be Applied Separately
Some growers assume that PGRs must be applied separately from other treatments, adding extra steps to the process. However, Dabbs points out that PGRs can be mixed with fungicides, insecticides, or even fertilizers in the same application, saving time and labor.
“Combining PGRs with other treatments, such as fungicides, helps streamline the process,” Dabbs explains. “Rather than making multiple trips across the greenhouse, you can apply everything in one go.” PGRs can also be added to fertigation tanks for drench applications, which allows growers to regulate plant growth while maintaining proper nutrition.
“By combining fertilization with PGR use, you can keep plants healthy and green while controlling their height,” Dabbs says. “It’s all about keeping plants in balance.”
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