Weed and feed on newly sown grass seed
If I spread weed 'n feed fertilizer on patches in my lawn where I have spread grass seed, will the "weed" portion of the fertilizer keep my grass seed from germinating? If so, how long after the seeds germinate can I safely use my fertilizer?
You are correct in that weed & feed might prevent seed germination. It is recommended to wait until your new grass is well established and you have mowed it a minimum of 4 times (usually 6 to 8 weeks) before applying a weed and feed fertilizer.