New Construction Seeding

[MGH PA]

We just seeded our new lawn a little over 3 weeks ago (about 1 acre). We hand spread a mix of Perennial Ryegrass, Creeping Red Fescue, and Kentucky Bluegrass (we're in zone 6a), then spread 150lbs of 10-10-10. We did not spread any mulching layer, but received timely rains, along with supplementing with sprinklers. Needless to say, we have great growth. I have about 96% coverage, and I'm at about 3.5-4" average height.

I see a lot of articles state that you should wait about 8 weeks to mow for the first time, but then it's usually stated that this time frame is to allow the grass to reach 4"+ height. So if my grass has reached the height requirements before the time frame, should I still let it go to establish the root structure? If I wait for 8 weeks at this rate, barring a drought, the grass will be VERY tall.

Thoughts?

 

[Ford850]

I mow my tall fescue at 3" or 3 1/2", but your mix usually does better when mowed a little lower than that. If this were mine, I would mow now at about 3" or 3 1/2" and continue to mow 'high' to encourage good roots. Mowing now will also avoid too many clippings or clumping which is hard on a new lawn. Then in mid August or so, when the days are getting shorter and the lawn starts coming back after the hot summer, I would lower to the height you plan to mow from now on.
Edit - I would wait a couple days for this first mowing until after our extreme heat comes through mid week.

 

[jay3534]

mow now to avoid clippings building up and smothering the tinder grass / use sharp blades / water only as needed as letting the ground to dry some will make the grass roots reach further down

 

[Wagtail]

I'd honestly wait the recommended 8 weeks... plants grow in two directions, after all, and letting the young roots mature & spread will be better in the long run.

If the grass height is a bother, then initially cut it twice. One pass high and then the last at the height you ideally want it at.

 

[Hay Dude]

I'd honestly wait the recommended 8 weeks... plants grow in two directions, after all, and letting the young roots mature & spread will be better in the long run.

If the grass height is a bother, then initially cut it twice. One pass high and then the last at the height you ideally want it at.

Agree. Wait for the roots to get more established. The clippings being long shouldn’t hurt anything since theres no build up of years of thatch. Be patient and youll allow those roots to survive the pounding of the mower tires.
I plant fields for hay, almost always in the fall. By the following spring, they are established and the roots are strong. Last year, I planted a field early spring and attempted to mow it late summer. It caused a lot of crown damage to the plants and I ended up with weeds overtaking the lawn.

 

[Ford850]

Mowing helps thicken the lawn so you don't want to let it get tall and leggy, allowing bare spots for weeds. Mowing acts the same as top pruning any plant, encouraging more shoots and thickening.

 

[kthompson]

Follow the seed company's recommendation. They want their product to perform well. Roots do need to be allow to develop strongly. Yes you do mow to help grass spread but that only works with some grasses who will spread. Some have to reseed to produce more hills of grass. Be sure your blades are sharp.

 

[MGH PA]

I think I will call the company. I don't care about the length (I don't have neighbors). I just don't want to negate all of my hard work.

 

[Ford850]

Don't worry too much about a perfect plan. The weather will have more affect on the lawn than when you cut it or at what height. You can see from the comments so far that there are several opinions on what each of us would do. I've put in many acres of lawn over the years so I'm comfortable with my methods and know what to expect for my grass types and the weather in my area. There's no right or wrong, other than keeping it watered if we don't get enough rain.

 

[ovrszd]

I agree. It'll be hard to irrigate an acre of lawn but it may come to that.

I've not had good luck seeding in the Spring. Always looks great until late July.

I seeded last year in late August on dry dusty dirt. Didn't mow it at all last Fall. Have a great lawn now.