· by Michael Blair, Nashville's Lawn Care
If the lawn was aerated and overseeded in early September, the new fescue is up by now and standing taller than the old grass around it. That is the point where people get nervous and either mow too early or wait so long the seedlings flop over and mat. Neither kills a lawn outright, but both cost you some of the seed you paid for. A seedling a few weeks old has roots barely deeper than the core holes it grew in, and the first few mowings are the roughest treatment it will get all autumn.
When the new grass is ready
Go by the height of the new blades, not the date on the seed bag. Once the seedlings stand about a third taller than the height you plan to keep the lawn at, they are ready, and cutting that third off is exactly the one-third rule applied to young grass. On a fescue lawn kept tall, that usually means waiting until the new growth is noticeably shaggy.
Give it a tug test first. Pinch a few seedlings and pull gently. If they slide out of the soil, the roots are not holding yet and a mower deck will do the same thing on a larger scale. If they tear at the blade instead, the roots have caught and the lawn can take a cut.
How to make the cut
Set the deck at the top of your normal range, or one notch higher. A dull blade shreds a seedling instead of slicing it, the torn tip browns within a day, and a lawn full of browned tips on young grass looks like the seed failed when it did not. Sharpen or swap the blade before this mow, not after.
Mow when the surface is dry and firm. Wet clay under a new lawn is soft, the wheels leave ruts, and a zero-turn pivoting in place will scrub seedlings straight out of the ground. Make wide, gentle turns, and if the property has a slope, mow across it rather than pivoting at the top and bottom.
- Wait for the tug test before the first cut
- Sharp blade, highest practical deck setting
- Dry ground only, and no tight pivots on the new areas
- Catch or mulch lightly so clippings do not smother the seedlings
Clippings, leaves and the blower
Clippings from the first few mowings are heavy with moisture, and a thick layer of them lying on young grass blocks light the way a wet towel would. Bagging the first cut or two is worth the extra trips to the curb. After that, fine clippings can go back down again.
Leaf drop starts in earnest in October, which is exactly when the new grass most needs the sun. A backpack blower on full power will move seedlings and loose soil along with the leaves, so turn it down over the seeded areas or mulch the leaves with the mower once the grass is established enough to mow at all. Leaving a mat of oak leaves sitting on new fescue for a couple of weeks can undo a good share of the renovation.
Everything else that walks on it
Keep dogs, kids and the car off the newly seeded parts for the first month if you can. Foot traffic compacts the soil the seedlings are rooting into, and a worn path across the yard is usually where the thinnest grass ends up next spring. A few stakes and some string along the worst route does more than asking everyone to remember.
Our crews treat a freshly overseeded lawn differently from the rest of the route for those first weeks: a lighter machine where we can use one, a higher deck, and no mowing when the ground is soft, even if that means coming back a day later. If a lawn has been seeded by someone else, tell whoever mows it the date, because they cannot see from the street that the grass is new.