Corn gluten meal will not harm grass seed at any time as long as the seed is kept moist. However, watering the corn gluten meal renders it useless as a weed seed killer.

Is corn gluten good for lawns?

Corn gluten meal gives the lawn a nice, natural dark green hue and seems to provide a large measure of disease resistance. So as a once-a-year fertilizer “if you can afford it” on your lawn, it's a great product. Also, if you're just using it as an organic fertilizer, you can reduce the rate to 10 lbs.

When should I apply corn gluten to my lawn?

Corn gluten is most effective when it attacks a weed just before germination or sprouting. Generally, weed germination, specifically for crabgrass, occurs in April and we recommend applying corn gluten in the first few weeks of the month or when forsythias begin to bloom.