James Altland, nursery crops specialist at OSU’s North Willamette Research and Extension Center in Aurora, spoke to his observations when corn gluten was used in plant nurseries as a pre-emergent herbicide.
A low-nutrient mulch such as well-rotted sawdust will benefit shrubs such as roses, azaleas, rhododendrons and hydrangeas. Lilies, dahlias and spring bulbs will do better with this type of mulching also. But be aware that composted sawdust or other fine organic material may contribute to weed growth.
In their trials with corn gluten meal, Hilgert and Cook found the following:
“I’ve seen nursery situations where the applied product caused a bad odor, as do some herbicides, and attracted rodents,” said Altland. “In nursery situations where the goal is complete weed suppression, my overall impression is that it doesn’t work that well.”
It is not clear why the commercial version of corn gluten meal used in OSU trials was not effective, said Cook. One possibility is that the product as formulated for sale has a short shelf life and loses potency during manufacture, shipping and storage. Further research needs to be done to test this hypothesis, he said.
The cornmeal in your pantry is made from ground-up corn kernels. This is what you use as an ingredient in recipes for cornbread and other dishes.
Since corn gluten meal has high levels of protein, nitrogen, and oils, it is also used for lawn fertilization and weed control purposes. It is sold in lawn and gardening stores rather than at your local grocery store.
How Do People Use Cornmeal as a Weed Killer?
Pre-emergent sprays work similarly to corn gluten meal by suppressing weed growth at the seed level, but it is a little different. A pre-emergent spray prevents seed germination. The seeds never develop roots or sprouts.
What is Cornmeal vs. Corn Gluten Meal?
There have been multiple studies on the use of corn gluten meal as an effective weed killer with mixed results. The primary issue with this method is the difficulty of applying it at just the right time to knock out the weed seeds.