Q: With all the heat and rain we have had this summer, we’ve struggled to keep up with the mowing. We’ve raised the mowing height to two and a half inches to reduce scalping. We typically mowed our fields once a week during the summer since the school fields are not used after spring graduation until practices start in late summer. With only once-a-week mowing, the grass grows so tall that our mower struggles to get through it, and I’m left with piles of clippings on top of the field. Is there anything I can do other than mowing it multiple times a week?
– Concerned coach and part-time turfgrass manager
A: This summer has been unusually hot, accompanied by frequent rainfall — conditions that bermudagrass has thrived in. With the addition of nitrogen fertilizer, growth has been so vigorous that one could almost watch the bermudagrass grow in real time. These conditions have been ideal for those renovating or replacing fields. However, for those managing established turf, the rapid growth has posed significant maintenance challenges. One way to manage this rapid growth is by mowing more frequently. Alternatively, you can use a plant growth regulator (PGR) to suppress turfgrass growth.
PGRs are chemical products that can be applied to turfgrass to inhibit vertical growth and significantly reduce mowing frequency for several weeks. Trinexapac-ethyl has been shown to reduce common and hybrid bermudagrass clipping weights by 50 percent. This effect is typically observed within seven days of application. Depending upon application rates, it usually provides suppression for about four weeks. The slowed growth will also dramatically reduce the chance of scalping. This can be a significant management advantage during periods of high rainfall that can result in missed mowing cycles.
PGRs have been used for more than 50 years, originally on roadsides and utility turfgrass to reduce mowing fre- quency. The early PGRs resulted in brown turfgrass and reduced stand density. While such damage was tolerable on roadsides, it was unacceptable for high-quality turfgrass. After trinexapac-ethyl (Primo MAXX) was introduced in the 1990s, the interest in PGR use went to an entirely new level, with greater acceptance on highly maintained turfgrasses such as those found on golf courses and athletic fields.
Adoption of PGRs in some segments of the turfgrass industry has been slow, partially due to product costs. Today, several affordable PGR options are available, including generic formulations of trinexapac-ethyl. The generic products have reduced the application price to less than $25 per acre (depending on product and application rate). So, most sports turf fields could be treated for less than $50. There are also granular PGR products now for those who do not have a sprayer.
PGRs not only reduce mowing frequency but also maintain turfgrass quality with fewer mowing cycles. There will be a decrease in clipping volumes, as well as reduced labor, fuel and equipment wear. Few products offer the dual benefit of saving time and money while also enhancing turfgrass quality. While the quality improvements from using PGRs can be impressive, their use does not eliminate the need for other cultural practices.
Most importantly for you, PGRs can keep you from needing to mow several times a week while maintaining lower mowing heights. For field managers struggling with excessive growth, PGRs offer a practical and cost-effective solution worth considering.
Grady Miller, Ph.D.
Professor and Extension Turf Specialist
North Carolina State University