Control weeds with corn gluten meal

Q. A neighbor down the street said he is going to use corn gluten meal on his garden to control weeds this year. What is it and is it safe to use in a vegetable garden?

A. Yes, you can use corn gluten meal in a vegetable garden even though its original use was to snub out pre-emergent weed seeds from germinating in lawns.

Corn gluten meal is a by-product of grain wet milling, sold as feed for cattle, hogs, poultry, fish and dogs with 60 percent protein coming from the corn. It was field tested in the 1980s and was proved to be a suppressant for controlling crab grass.

Researched by Nick Christian out of the University of Iowa, the product was patented in the early 1990s and sold as an organic pre-emergent herbicide for broad-leaved weeds, purslane, plantain, dandelion, dock, barnyard grass, Bermuda grass, lambs quarters, foxtail and many others.

Corn gluten meal, in a powdery form, is organic and nontoxic. It has an N-P-K (nitrogen, potash, potassium) of 9-1-0, where nitrogen gives you the healthier, dense, green grass.

Several applications may be required and timely applications are critical. If the weed seeds have germinated, apply in the fall or the following year because once the root of a seed has started to grow, an application may not work.

Apply corn gluten meal when there is no prediction of rain for at least three to five days after application. Spray lightly with water and let it do its job by drying and snuffing out the emergence of germinating weed seeds. As a gauge, this would be early spring, when the ground has warmed up and the forsythia and daffodils are blooming.

Spread a minimum of 10 pounds per 1,000 square feet, using a spreader. Be aware it will affect all seeds. Do not sow grass, flower or vegetable seeds while using corn gluten meal. You may plant transplants or mature plants.

In gardens with paths, spread the corn gluten in the paths to keep weed seeds from germinating.

Corn gluten meal is sold by many brands. It's sold in 10- to 40-pound bags, ranging in price from $20 to $50. It may be found in garden centers with the herbicides; otherwise, ask the clerk.

It comes unprocessed (powdery), granulated and pelletized. It's recommended that corn gluten meal with 60 percent protein is most effective. Always read the directions on the use of the product you purchased.

It may take several applications and two years to see good results. Manual weeding may be needed to remove established weeds.

- Joan Jeske

• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 Monday, Wednesday and Saturday or (847) 201-4176, ext. 14, on Fridays.