Weed And Feed Vs Overseeding . An application of gordon’s trimec or speedzone can be applied 28 days after grass seed germination. Stay with high quality seed. Overseeding with Perennial Ryegrass Green Keeper from greenkeeperaz.com Once you’ve got your compost spread evenly, rake it lightly so it can mix with the soil and blend into the aeration holes. The herbicide in the soil will attack every type of grass seed. Avoid using weed and feed products on new lawns.