Corn gluten meal (CGM) is a natural substitute for synthetic pre-emergence herbicides. Pre-emergence herbicides attack seeds while they’re still in the ground, before the seedlings emerge from the soil. CGM is a by-product of commercial corn milling that contains the protein fraction of the corn. Its use poses no health risk to people or animals. In fact, because it is 60% protein, corn gluten meal is used as feed for cattle, poultry, fish, and dogs. In addition to the 60% protein, corn gluten meal is 10% nitrogen, by weight. Source: CORN GLUTEN MEAL: A NATURAL PRE-EMERGENCE HERBICIDE – University of Minnesota Extension.
From what I read, timing is the key. Time is quickly running out for a spring application. Some people may think it could be a little late this spring. Corn gluten meal works best when weeds have not started growing yet. I am just starting to see dandelions and other weeds coming up in my neighborhood with the recent warm weather. Also, you want to make sure and apply this product when the conditions are drier as opposed to wet.
If you are looking for a natural pre-emergent. Corn gluten meal is a good source of nitrogen, 10% and a natural weed preventer. Great for small spaces. Could be a bit pricey for entire lawn spaces.