CGM targets a range of plants include small-seeded annual and perennial herbs. It is most frequently used in lawns, but may be applied to gardens and fields as well.
The corn gluten meal breaks down over time as an organic nitrogen source (NPK value of 10-0-0).
Proteins in CGM inhibit root formation on newly-germinated seeds, killing the plant. Applications must be timed so that the CGM is present and effective as seeds are germinating.
Applied using a spreader or even by hand: the material is essentially harmless if not inhaled, and is, in fact, edible (though not particularly palatable).
On lawns, CGM is applied in early spring (usually timed phenologically by the blooming of Crocus or Forsythia, and again in the autumn. If the lawn is overseeded, CGM should either be applied at least 6 weeks before sowing, or 2 weeks afterwards.
Very safe to use, non-toxic. Should not be applied to areas where it's likely to wash directly into watersheds (it is a nitrogen source), but otherwise ecologically safe.
Large-seeded weeds seem unaffected.
Testing for affected species is ongoing, but confirmed species include: