I just finished putting corn gluten meal on my lawn. I do it every spring and fall. In the spring it acts as an organic, pre-emergent weed control that stops seeds from growing. This includes weeds and grass, so it cannot be put on newly planted grass. Then again, in most places in the northern United States you should only be planting grass in the fall.
The trick with corn gluten meal, or almost any pre-emergent herbicide, is timing. Put it down too late and the weeds will already be growing. The fertilizer then helps the grass and the weeds. Put it down too early and the protection it provides can run out.
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