Changing mowing lines is a common occurrence for golf course superintendents. Cleanup passes drift from year to year. Bunkers magically end up farther away from fairways or approaches than originally intended. Or maybe increasing closely mown turf throughout the course was a maintenance goal. Whatever the reason, if the altered area is not sodded out, it can take a few years for the turf to adapt to its new mowing height. This is especially true if the grass is Poa annua.
A recent Green Section Record article on Poa annua discussed some unique genetic traits that this turf species has. Studies have shown that Poa annua plants “remember” how their parent plants were treated. This transgenerational memory can be perpetuated if the same cultural practices – like mowing height – are continued for any length of time. However, if cultural practices change, it can take years for the offspring plants to forget how they were programmed to respond. This has been evident on many a Course Consulting Service visit.
I have seen Poa annua rough that was mowed down to fairway or approach height struggle to fill in a dense canopy during the first few seasons after the transition. The same is true when Poa annua approach or fairway turf is grown up to rough height and never seems to get quite as tall as the original Poa annua rough right next to it. Unfortunately, there is not much a superintendent can do to encourage Poa annua plants to change how they are genetically programmed to behave.
It is believed that after two to four years, this transgenerational memory will fade away and the turf will adapt to its new normal. In the meantime, introducing other grasses into the mix can help with density and uniformity issues. Understanding this unique phenomenon can help set realistic expectations when considering a substantial mowing height change in Poa annua. Depending on your situation, it might make more sense to sod out these areas for a quicker transition. But no matter what you decide, it’s clear that this is just one more reason for us to marvel at Poa annua.
West Region Agronomists:
Brian Whitlark, regional director – bwhitlark@usga.org
Cory Isom, senior consulting agronomist – cisom@usga.org