There’s a story circulating the internet and being shared on multiple Facebook pages promoting cornmeal for weed control in gardens, lawns and flowerbeds. It’s highly deceptive and can lead to widespread disappointment.
It started well enough when Iowa State University innocently discovered in 1991 that corn gluten meal (abbreviated CGM), which is a byproduct of wet milling of corn, prevented some weed seeds from growing. Iowa State reported “research revealed that a naturally occurring compound in the protein faction of CGM had an inhibitory effect on … germinating seeds. In 1991, a patent was granted on CGM as a natural, preemergence herbicide. As a preemergence herbicide, CGM only controls germinating seeds and has no effect on weeds that are already established.” But they further indicate “CGM has some limitations and variability as an herbicide. For example, results may not be obvious after a single application the first season.”
Based on the hope that an organic weed preventer had finally been found, commercial products were introduced, and reports went wild that corn gluten meal as an active ingredient was a successful new weed control method. I wrote about it as well, as a new option.
In the meantime, the product wasn’t working for many gardeners, and other research institutions began to investigate corn gluten meal as an active ingredient. Washington State University’s “The Myth of Weed-killing Gluten” says “Researchers at the Mt. Vernon station found no differences in weed control on field-grown strawberries” that were treated with corn gluten meal versus untreated.
Ohio State University was even more direct, in their article “Corn Gluten Meal Did Not Prevent Weeds from Germinating in OSU Study,” which says “Corn gluten meal did not control any weeds in any trials under any circumstances over a two-year period. They found no evidence of pre- or post-emergence weed control in any of their trials.” Ohio State University was unable to duplicate the research from Iowa State on which the whole CGM publicity was based.
A big deception in the internet story promoting cornmeal for weed control is that cornmeal found on our pantry shelves isn’t corn gluten meal. Corn meal is made from dry-ground corn, and isn’t a byproduct of wet milling, as is CGM. So the internet story of grabbing the Quaker Corn Meal off the shelf and solving weed problems isn’t accurate, even if the corn product CGM were effective.
Is there a future in Corn Gluten Meal for weed control? I don’t know, but currently it’s looking less promising than initially thought.