Why timing is not the real question
A common myth is that you have to let a ground stump sit for a year before you can plant grass. That comes from homeowners seeding straight into a chip pile, watching it fail, and blaming the timing. The problem is not time. It's that wood chip is a terrible seedbed. Fix the seedbed and you can seed inside a week of grinding.
The four-step method
Step 1. Rake the chip out. Pull the wood chip and dirt mixture out of the grind pit and either pile it for mulch elsewhere or haul it off. You want to see the walls of the original hole again.
Step 2. Fill with clean topsoil. Backfill with screened topsoil to about an inch above the surrounding grade. New fill always settles, so a slight crown is what you want. In our piedmont clay we mix in one part compost to three parts topsoil so the fill drains like the surrounding yard.
Step 3. Seed at the right season. In Cabarrus County, tall fescue goes down between mid-September and mid-October, watered daily for the first two weeks. Bermuda gets sprigged or plugged between late April and mid-June. Skip the off-season and the effort is wasted.
Step 4. Water and re-topdress. Keep the seedbed moist for three weeks. After germination, topdress with a quarter inch of soil every four weeks for the first season to compensate for settling as the residual chip under the fill decomposes.
What kills a stump-spot lawn
- Seeding onto raw grind chip. The wood pulls water and nitrogen away from the seedlings.
- Skipping the topdress schedule. The spot sinks, water pools, and the new grass drowns.
- Seeding in July. Fescue in a piedmont summer dies faster than you can water it.
Do the prep right and the spot blends into the yard by the following spring.