Corn Gluten Meal
Compiled by Sue Flinders-Adams, Haliburton Master Gardener
Corn Gluten Meal (CGM) is a natural byproduct of wet-milling corn during the production of corn syrup. It is used in the production of taco shells, pet foods, corn chips and animal feed. A 20 lb bag treats 1000 sq. ft.
Corn Gluten Meal is both a pre-emergent herbicide and a natural source of Nitrogen fertilizer, making it an all-natural weed and feed product. It inhibits the germination of seeds by significantly increasing the level of proteins in the soil, causing newly germinated plants to die. It has an N-P-K ratio of 10-0-0. CGM is used primarily to control crabgrass and dandelions, but will also inhibit germination of other weeds.
When to apply CGM: Three times a year is best but the spring and fall applications are the most important. Fall application prevents weed root systems from establishing before winter, while the spring application will control the germination of weed seeds from the previous fall. The spring application should be done after the forsythia blooms and before the lilac blooms. The summer application should be from the middle to the end of June, which will reduce the weed seeds that blow in during late May.
In July to mid-August, the lawn will be dormant or semi-dormant depending on the temperature and rainfall. Let the lawn go dormant by not giving it additional water. This reduces the survival of recently germinated weed seeds and the eggs of lawn insects.
How to apply CGM to your lawn: It is applied to the soil surface for lawn weed control. Broadcast the product using a fertilizer spreader at the recommended application rate. Water the product thoroughly after application to press it to the soil surface and then let it dry out. The drying out puts the newly germinated seed in further stress. CGM will still be effective if you do not have a chance to water your lawn immediately after applying it, because the proteins in the CGM are released every time it rains or the lawn is watered, until the pellets decompose.
New Plantings: Mix CGM into the top 1/4" of soil before transplanting container grown annuals, perennials or vegetables. These plants will not be harmed by the CGM because they have a large, strong root system.
CGM in pellet form is easier to apply than the powder form; it will not cake when it is watered and will not blow away upon application.
How It Works: The natural plant proteins (dipeptide) in corn gluten meal stops root growth when seeds germinate causing the plants to die. These proteins are toxic to root growth in seedlings. The effectiveness increases if the soil dries out shortly after germination, because the plant will be unable to regrow a root system before it dies.
Timing is critical for CGM! If it is applied too late in the spring, when weeds are established, then the nitrogen content, which is a fertilizer, makes them into super-weeds!
Corn Gluten Meal is available under several brand names: Amaizeingly Green, TurfMaize, and Scott’s Turf Builder Weed Prevent. Be sure that you are getting 100% corn gluten meal. It is not as effective as an additive to other fertilizers. Master Gardeners of Ontario does not endorse any brand. I am just making the information available.
Dr. Nick Christians developed Corn Gluten Meal as a pre-emergent weed inhibitor in the early 1990’s at the University of Iowa. For more information visit: