There is no hard rule or height. The general consensus is to go a little lower (1/2") for example then your normal HOC. Don't just do this for your last cut, but for your last 3 or 4 to allow your grass to adjust, so now is the right time for sure, to start..

 

^+1

 

I took my fescue from 3.5" to 1.75". It took about a month to green back up and leaf out. It was mostly just brown stems. Of course, put down some fert to help it grow. I like the shorter feel and look as it doesn't mat much especially when the snow comes. I'll keep this height until late spring when summer heat starts coming. I don't water in the summer.

 

According to my 2018 journal notes, I lowered HOC to 3.25" by early Nov and grass growth had slowed by end of that month. Then early Dec the deer & rabbits started eating the grass blades and ate down near to the crown. So I guess you can say that the wildlife did my last mow and took it to an appropriate end of season HOC.

 

I verticut and overseeded on 9/2, first mowed it on 9/13 and have been mowing it twice a week since. On 9/13 my yard was probably 8" or taller and I cut it to 4.5

I have mowed it 2-3 times a week and have it down to 2.75". That's as low as I think I would take it, I keep my lawn at 4" or higher May through September due to the heat.

 

Maybe someone will do an experiment on this. Do a strip at 4, 3, 2, etc. and see what happens. I don't think it matters but would love to be proven wrong.

 

@tgreen I did an experiment couple of years ago. It really did not matter. I did fall nitrogen vs. only late nitrogen (aka winterizer) in december and 3in hoc vs ~1.5in hoc. The 1.5in looked better during the winter with the snow vs the 3in. It looked greener and it looked to green up faster, but it was not really any different than the 3in. The 3in with the longer blades made the tips dry out and look brown vs the stuff closer to the warmer ground. In spring the shorter looks greener because it has less brown stuff, but both areas greened up at the same time. After a few mows they looked the same.

 

@tgreen I did an experiment couple of years ago. It really did not matter. I did fall nitrogen vs. only late nitrogen (aka winterizer) in december and 3in hoc vs ~1.5in hoc. The 1.5in looked better during the winter with the snow vs the 3in. It looked greener and it looked to green up faster, but it was not really any different than the 3in. The 3in with the longer blades made the tips dry out and look brown vs the stuff closer to the warmer ground. In spring the shorter looks greener because it has less brown stuff, but both areas greened up at the same time. After a few mows they looked the same.

Thanks g-man! Nothing beats someone that has run an experiment first-hand. Good info.