Christians discovered corn gluten meal's herbicidal activities more than a decade ago while using leftover cornmeal to grow a pathogen found on golf course turf. CGM is labeled for use on turf, field crops, and home gardens. Among the weeds controlled with pre-emergent application of the product are crabgrass, dandelions, smart weed, redroot pigweed, purslane, lambsquarters, foxtail, and barnyard grass. Christians is now looking at the effect of corn gluten meal on garden seeds. However, shallow-seeded species such as carrots and lettuce seem to incur damage.
Most labels call for the herbicide to be applied pre-emerge in spring and fall.
Christians says the best approach is to first try the product on a small area of your yard or garden. Garden seed can be sown slightly deeper than usual and CGM broadcast uniformly over the area and lightly raked into the surface, then watered in well. The CGM then inhibits growth of the weed seedlings' root tips. Potential problems with CGM stem from the fact that extensive moisture and microbial soil activity can reduce its effectiveness. The other drawback is the higher cost of CGM as compared with other weed and feed products.