[g-man]

There is a long thread on PGR on cool season lawns here: PGR + Cool Season Grass

Amount to use depends on your HOC. I suggest keeping a control section in a corner of your property (an area without any PGR), so you can test the amount of suppression you get. Too much can cause problems too, more so during a humid summer days.

 

[g-man]

There is no scientific study conducted on pgr application rates/gdd on rough height turf so your guessing just like the rest of us on pgr reapplication intervals. Looks to be a good tool for logging fert/ pesticide applications.

Dr. Kreuser has values for cool season athletic fields hoc as part of the the greenkeeperapp. We saved the values before the site switched to a paid subscription. Also, the GDD is mainly a function on the amount used and not so much of hoc, per his studies.