Corn Gluten Meal – A Natural Pre-Emergence Herbicide
June 15, 2013
Spring is alive and well and the garden is now beginning to bloom. Good times for all, including the weeds. As they say with the good comes some bad. One pre-emergent herbicide that has become popular in the past twenty plus years is an organic called Corn Gluten Meal.
Corn Gluten Meal is a bi-product of the commercial corn milling industry. Corn Gluten Meal is the protein component of the corn. Its use as an herbicide was discovered at Iowa State University in 1991, when it was noticed that an application of Corn Gluten Meal prevented grass seeds from sprouting. Continued studies demonstrated that it also effectively prevented other seeds from sprouting, including seeds from many weeds such as crabgrass, chickweed, and even dandelions.
Corn Gluten Meal can be applied to turf as well as garden beds. Applying it to turf can be rather expensive, depending on the size of your yard. It’s also important to time the application well. One rule of thumb is to spread the granular herbicide when the Forsythia is blooming in the north and the dogwood is blooming in the south. An application in mid-August has also proven to be effective.
As for the garden, a method I practice is to spread a layer of Corn Gluten Meal just prior to mulching a planting bed. Somewhat of tag team approach, as the Corn Gluten Meal will prevent annual weed seeds from sprouting and the mulch will suppress perennial weeds and others from becoming established. In a vegetable or annual flower garden wait until the seedlings are up and growing before applying Corn Gluten Meal.
It is important to note that Corn Gluten Meal is only effective against weed seeds. It will have no effect on already existing weeds or perennial weeds. My perspective on the use of Corn Gluten Meal is that it is a nice tool to have in your gardening tool kit. The best practice to keeping the weeds at bay in your garden is to keep 3-4” of mulch in your planting beds and consistently weed the beds. If you keep a good practice of this habit over time your weeds will diminish significantly and the plants you want in your garden will be much more happy and healthy.