Corn gluten meal (CGM) has no effect on established weeds; its active ingredient inhibits seed germination, any seed germination. Therefore, applying it after the weeds are up and growing will only feed them. CGM is not selective and can inhibit germination of any plant seed including desirable plant seeds. Though it may be effective in the Midwestern United States., CGM is not as effective in other climate zones, i.e. the western U.S. There are no scientific data from field trials in the western U.S. to support the use of CGM in weed control. Finally, other environmentally friendly weed-control treatments (such as sub-irrigation, mulch, or soil solarization) are cheaper and often more effective than CGM.

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