How many times have you said “learn from your mistakes.” Well, that is exactly what Nick Christians, a research at Iowa State University did. His mistake was spilling corn gluten meal (CGM) while working in the research fields. He was using the CGM as an ingredient in fertilizer. He noticed that in the spot where he spilled the CGM, no seed would germinate. Aha! He learned from his mistake that CGM is not only a great source of nitrogen for plants but may also work as a pre-emergent weed seed control!
Corn gluten meal is a fine powder that is a byproduct of the corn milling process. Traditionally it had always been used as a supplement in hog feed. There is a natural protein in CGM that is a good nutrient for lawns and gardens and also an effective at suppressing new weed growth. Although we cannot refer to CGM as Organic because it is not made from organically grown corn, it is non-toxic and safe.
How does corn gluten meal work? The Nitrogen-Phosphorus-Potassium (N-P-K) ratio of corn gluten is 10-1-0, or 10% nitrogen by weight. The reason why it is a natural weed suppressant when applied at 20 pounds per 1000 square feet is because as soon as the seed germinates, the tender root is dried out. Combined, these qualities make CGM an ideal weed and feed product.
Does corn gluten meal hurt my plants? When applied at the recommend rate of 20lbs/1000 square feet, CGM only works by inhibiting root formation at the time of germination, it does not harm roots of mature or transplanted plants.
How do I apply Corn Gluten Meal? We recommend using a pelletized form of CGM. The other two options are unprocessed or granulated—both of the latter options are fine/powdery and are more cumbersome to apply. Pellatized CGM can be broadcast through a spreader or by hand. Using it in the garden or on the lawn during spring will provide weed suppression through the early summer. In our area, that is the time of year that is most critical for weed germination. When applying CGM, it is important to not apply any other fertilizer for 4-8 weeks as the level of nitrogen in the CGM is on the high side.
What weeds are controlled by Corn Gluten Meal? Included in the list of seeds that CGM effectively controls are: Crabgrass, creeping bentgrass, dandelions, purslane, lambs quarter, foxtail, and more. It is important to not apply CGM in areas that you plan to grow things from seed within the following 6-8 weeks. This includes seeds for lawns, flowers, and food gardens.
Tips for using Corn Gluten Meal: In south eastern Wisconsin it is only necessary to apply CGM once per year, in the spring. Since corn gluten effectively suppresses weeds for about 6 weeks, timing is important. My visual que is sometime after the Forsythia bloom but before the Lilac shrubs blossom. These two plants indicate that soil temperatures are warming and conditions are right for seed germination. The recommended and effective rate for seed suppression is 20 lbs per 1000 square feet. For best results, rain or a light sprinkling within 48 hours after application is good—CGM will not be effective until it dissolves and makes a film over the soil.
Corn Gluten is a safe and effective weed suppression for your lawn and garden.
By: Loriena Harrington, Horticulturist