You may have seen all the hype on Pinterest and Google and even Facebook, but if you have not read the whole article you may be misled into thinking that you can just go pour some cornmeal on your garden and it will work. That is not the case.
What is actually used is corn gluten meal. This is a bi-product of the wet milling process used to produce corn starch and corn syrup. So you will not be able to buy a bag of regular cornmeal from the baking isle of the grocery store and have any kind of weed preventing results.
So now you may be asking where you can buy corn gluten meal. Most farm supply centers and hardware stores stock it in many forms under many labels. It is also available on Amazon. However, not all corn gluten meal is of the same quality. You will want to purchase those that have at least 60% protein. As lesser percentages do not have the herbicidal properties needed to be effective as a pre-emergent. True corn gluten meal will be labeled as a pre-emergent herbicide and is expensive when compared to lower grade products. You can rest assured that the other products that are marketed as feed grade or as distillers grain are not going to give you the results you seek. The corn gluten meal is getting a bit of a bad rap because most people are opting for the cheaper feed quality and there is not sufficient protein content in these cheaper products to actually be effective. So if you choose to use the corn gluten meal, take a moment to read the labeling thoroughly.
How you apply the corn gluten meal to your yard or garden can influence its effectiveness. There must be a perfect combination of circumstances in order for it to work. If there is too much water, it can leach the protein from the soil and render the gluten to a neutral state. If there is not enough water and the result is very dry soil the proteins may not be activated enough to reach the roots of the germinating seed. ½ cup of corn gluten meal distributed over a square yard of land is the rate of distribution that is preferred. Keep in mind that herbicides are non-discriminatory. So if you have grass seed, or plant seeds of any sort that you intend to keep, nurture and grow to maturity do not use this or any other pre-emergent until those seeds have germinated and produced a good root system. It is recommended that the corn gluten meal be applied when the forsythia starts to bloom as this is the time just before crabgrass starts to grow. Due to the nitrogen content in the corn gluten meal, you must keep in mind that it will not only aid your current lawn and plantings in their growth but it will also aid the growth of any weeds that already exist. Also, if you get a significant amount of rain you will need to reapply the corn gluten meal for it to continue to work. So all the hype that is circulating on the internet about the herbicidal benefits of cornmeal is FALSE.
Even some of the hype about the corn gluten meal is not as glamorous and perfect as some would have you believe. While it does work and it is a great option for organic gardening it is expensive and it only works under the right application and circumstances. So do not believe everything you read. Do some research on the product for yourself and decide what is right for your specific needs. We must note that corn gluten meal is not harmful to pets or children unless there is a corn allergy present in either.