By Bev Johnson

Master Gardener

If you want a healthy, weed- free lawn but are concerned about the effects of herbicides and synthetic fertilizers on your environment, especially if you live on a lake, there is an effective, all-natural product that will ease your conscience and reduce weed growth in your lawn- corn gluten meal.

Corn gluten meal is a natural by-product from the wet milling of corn. It contains 60 percent protein and is used as a supplement in feeds for livestock, poultry, and pets.

Who would ever think to use cattle feed on the grass? Well, it happened by accident. In 1985, Nick Christians, professor of horticulture at Iowa State University was using the stuff as a growth media in a study of turf grass diseases. He wasn’t getting the results he was expecting as the CGM actually reduced the germination of his grass seeds. Now, of course, he had to find out what was happening to his grass.

His research revealed that a naturally occurring compound in the protein faction of CGM prevented root formation of germinating seeds. In 1991, he was granted a patent on the stuff as a natural, pre-emergence herbicide for use on all crops. As a pre-emergence herbicide, it only controls germinating seeds and has no effect on already established weeds. It is the first effective “organic” herbicide.

It comes in 2 forms, granulated and powdered. The powder is sold at mills as cattle feed and is cheaper. The granulated is marketed under several trade names and is easier to apply.

Timing of application is critical for good weed control. It needs to be on the lawn 3 to 5 weeks before the crabgrass seeds and other annual weeds germinate. That usually is in late March or early April. Old Ma Nature decided, not this year. Crabgrass needs a specific soil temperature to germinate. An easy way to determine the proper soil temperature is fairly easy. Apply the first application when the daffodil blooms just show color. The second when the lilac flowers just start to show color. These two bloom when the soil is at the ideal temperature for the crabgrass to germinate.

Spread the CGM at a rate of 20 pounds per 1,000 square feet and water it in. Then let the soil dry out so the sprouted weed seedlings die. Apply again in mid-august to control late season annual weeds.

Besides its high protein content, CGM also contains 10 percent nitrogen by volume making it an excellent slow-release fertilizer for lawns. It makes the grass thicker resulting in fewer places for weed seeds to germinate.

You can use this stuff in established perennial flower gardens. Use the named CGM in the vegetable garden after transplants and seedlings are well established, as, of course, it will kill any seeds that try to germinate. The commercial CGM will have label recommendations as to application rates. 

Corn gluten meal does have some limitations and viability as a herbicide. You may not see much result after a single application the first season. Control improves every year it is used on lawns. It is often more expensive than the artificial stuff, and it can be less effective if there is extensive rains right after application. None the less, it will not kill fish if washed into the lake like some fertilizers do. It also doesn’t promote lake grass growth and it is organic.