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Corn Gluten Meal as a Natural Pre-Emergent Herbicide for your Organic Lawn and Garden

written by: J.C. Wilkinson•edited by: Lindsay Evans•updated: 8/18/2010

If you're looking for a safe and effective natural pre-emergent herbicide for your organic lawn or garden, corn gluten meal may just be what you need.

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    If you are looking for natural weed control for your organic lawn and garden you know how difficult it is to find. Most natural weed control is post-emergent, meaning the weeds must be sprayed after they have germinated. Corn gluten meal has been around a while, but is gaining in popularity as a natural pre-emergent herbicide for organic lawns and home gardens.

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    What is Corn Gluten Meal?

    Corn gluten meal is a byproduct of the corn wet milling process. It was discovered in 1986 by Iowa State University researchers who were conducting experiments on pythium fungus in turf grass. The addition of corn meal didn't help the pythium, but it was discovered that it affected the growth of bentgrass in the experimental turf plots. Research began in earnest on its herbicidal properties, and it was patented in 1991, with additional patents in 1993. It was registered with the Environmental Protection Agency in 1994 as a herbicide. After the original patent, it was discovered that using the hydrolyzed proteins from corn and other grains controlled weeds better than the corn gluten meal alone, however, the sprayables were discovered to be less stable than the meal.

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    How Does it Work?

    Corn gluten meal works by inhibiting root formation in weeds at the time of germination. It doesn't inhibit roots of mature plants or transplants unless it is used at a very high rate of 80 pounds/1000 sq. ft. or more. Weeds germinate and form a shoot, but no root. A short drying period is required after germination, because too much water will allow the plants to recover and form roots.

    Corn gluten meal has no post-emergence effect on established weeds and, due to it's 10% nitrogen content, it actually acts as a fertilizer for them. It does not work well with seeded crops unless they are seeded very deeply, radishes being the exception. When used in an organic home garden, it is recommended that you use transplants or mature plants, or do not apply the meal until the plants are well established.

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    Where Can You Use Corn Gluten Meal?

    The main use of corn gluten meal as a natural herbicide is in turf grass. It is recommended that you apply at the rate of 20 lbs./1000 sq. ft. twice a year, in spring and fall.

    Corn gluten meal is also approved for home use as a natural herbicide in ornamental and vegetable beds.

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    How Do You Apply Corn Gluten Meal?

    Timing is essential in the use of corn gluten meal. It must be applied before the targeted weed emerges above the soil. Since a drying period is required after application, you should make sure no rain is forecast for a few days after application.

    Rates vary depending on the crop and the weeds targeted. A general recommendation is 20 lbs. per 1000 sq. ft.

    Work the corn gluten meal into the soil to a depth of 1 inch, and water to a depth of 1/4 inch. The drying period may vary, but the soil must be allowed to dry in order to kill the weeds. Keep in mind that moisture is necessary for activation of the material, yet extended wet spells can reduce its effectiveness.

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    Which Weeds Does Corn Gluten Meal Control?

    Crabgrass control is a major focus in use of corn gluten on lawns, however it also controls creeping bentgrass, smart weed, dandelions, redroot bigweed, purslane, lambsquarter, foxtail, barnyard grass, and Bermuda grass.

    Corn gluten meal is available from garden centers and online distributors. While it's not the cheapest way to control weeds, it is a great addition to your organic lawn and garden care arsenal.