We used to recommend holding off on applying starter fertilizer until 5–7 days after germination (or when you can safely walk on the lawn). The idea was to avoid fuelling a surge of top growth in your existing lawn while your new seed was still sitting on the surface—an approach you’ll hear from seasoned lawn enthusiasts more than in generic guides.
That advice is still solid if you’re using a standard big-box starter fertilizer that relies heavily on fast-release nitrogen (e.g., urea or ammoniacal N). Those formulas can fuel established turf quickly, which isn’t ideal when seedlings are just getting started and competing for light, moisture, and nutrients.
However, SeedLaunch Pro™ (our starter fertilizer) was engineered specifically for seeding projects to address this issue and is designed to be applied at the time of seeding. Meaning you apply it right before or right after you throw down your grass seed. This applies to overseeding or starting a new lawn from bare soil.
If you’re not using SeedLaunch Pro™ or a professional fertilizer from the golf course industry, the “wait-until-germination” method remains a great way to keep things balanced with typical retail fertilizers. In all cases, follow the label rate and keep the seedbed consistently moist—your preparation and watering do most of the work; fertilizer helps you get the most out of it.