Corn Gluten Meal: A Natural Herbicide
Kathy Powell, Portage Co. Master Gardener

Controlling weeds in an environmentally sound way can be a challenge inyour garden and lawn. Corn gluten meal is a natural product that can safely inhibit germination of grass and weed seeds.

In 1985, Dr. Nick Christians, of Iowa State University (ISU), accidentally discovered that corn gluten had preemergence herbicide activity. The control plot of a turf fungal study showed thin seeded grass stands when pure corn gluten was used. Further study by Dr. Christians and his graduate students lead to 4 patents on corn gluten and its active components over the last 15 years. Currently over 20 companies are licensed by ISU to sell corn gluten as a natural herbicide (US Patent 5,030,268; Re 34,594).

Corn gluten is a by-product of wet milling process to make cornstarch. It is an animal feed for cattle, poultry, other livestock, fish and some dog foods. It also contains naturally occurring substances, which inhibit the growth of seed's tiny feeder roots by causing a break down in the cell wall. The seedlings struggle to get enough moisture, which causes them to die before they ever have a change to take hold. When used as directed, corn gluten acts as a preemergent natural herbicide that will not harm beneficial insects, soil organisms, pond or stream life. It is also safe around pets and children.

Since corn gluten kills only the roots of sprouting seeds, it can be used around transplants and established vegetables, flowers, fruit, shrubs and lawns. It can be used even up to the day of harvest. Once vegetable or flower seedlings have true leaves, it is then safe to apply corn gluten.

Corn gluten has another benefit. It is 10% nitrogen by weight in a slow release form. As a 10-0-0 fertilizer it can inhibit weed germination and feed your lawn and garden nitrogen. (Additional supplements of phosphorous and potassium may be needed, based on a soil test.)

The only potential hazard that is documented so far is potential allergic reaction from inhalation of dust with certain individuals.

Facts

• Corn gluten is a fine yellow powder, usually pelletized for easier application.

• It comes in 5 lb bags, but a 25 lb bag (blended with bone meal and potassium sulfate from the organically certified Idaho mine) will be available this fall from Necessary Organics.

• It is available at local stores, by mail order, or on the Internet under various brand names including:

Name/Distributors	Licensed Manufacturer	Phone
BioWeed	Bioscape, Inc. 4381 Bodega Avenue Petaluma, California, 94952	707-781-9233
Concern Weed Prevention Plus	Necessary Organics 8906 Wentworth Avenue South Bloomington, MN 55420	800-468-2472
Corn Gluten Meal Weed Control	Safe Earth Lawn & Gardens 900 52nd St. W. Des Moines, IA 50265	515-222-1997
Corn Weed Blocker	Greenfire 2527A Hwy 32 West  Chico CA 95973	530-895-8301  800-895-8307
DynaWeed  American NaturalProducts Co. Planet Natural	Soil Technologies Corp. 2103 185th Street Fairfield, IA 52556	515-472-3963 800-221-7645
Earth Friendly	Cereal Byproducts, Inc. Mount Prospect, IL	847-818-1550
GreenSense	Rhode's Services, Inc. 1651 Wall Street Garland, TX 75041	972-864-1934
Organic WEEDZSTOP	Fertrell, Inc. P.O. Box 265 Bambridge, PA 17502	717-367-1566
ProPac	Manning Agricultural Center, Inc. 619 Julia St. Manning, IA 51455	800-248-4409
Safe Earth Natural Weed Control	Safe Earth Lawn & Gardens 900 52nd St. W. Des Moines, IA 50265	515-222-1997
Safe 'N Simple	Blue Seal Feeds P.0. Box 8000 Londonberry, NH 03053	603-437-3400 800-367-2730
Safeway	Lawn Ranger New Buffalo, MI	616-469-0667
SUPER ORGANIC "G"	Winton Graf  Bloomington, MN	612-887-0068
Suppressa Totally Organic Product Supply	Hardesty Organic Supply 252 Hedge Road Menlo Park, CA 94025	650-325-5959
Tiger By The Tail	Greener Pastures Minneapolis, MN	651-646-2900 800-798-1069
WeedFREE	Butterfield Gardens Glen Ellyn, IL	630-393-1062
Weed-Stopper Plus	Walt's Organic Fertilizer Co. 1528 NW Leary Way Seattle, WA 98107	206-297-9092 206-783-6685
W.O.W! (for without weed) W.O.W! Plus Granulated W.O.W!	Garden's Alive! 5100 Schenley Place Lawrenceburg, IN 47025	812-537-8650 812-537-8652

• It is patented as a preemergent herbicide. Feed mills can not legally sell it for this purpose unless it is licensed by ISU.

• Corn gluten results in less weed seed carryover in soil and added nitrogen to feed plants.

• Areas that gardeners want annuals and perennials to reseed should not use corn gluten until after the seedlings are up and have true leaves.

Effectiveness

• Corn gluten works on seeds not established plants. It will not kill a dandelion plant.

• It has reduced crabgrass by 86% the first year and 98% the second year provided recommended rates are applied in both spring and fall. Dandelion infestations were reduced 100% in plots treated for 4 years in spring and fall.

• Plants tested to date for susceptibility = 23 and include: barnyard grass, smooth crabgrass, curly dock, green & yellow, black nightshade, orchard grass, shattercane, purslane, wooly cupgrass, giant foxtail, lambsquarters, buckhorn, quackgrass, velvetleaf, annual bluegrass, dandelions, creeping bentgrass, black medic, redroot pigweed, catchweed bedstraw, & other common garden weeds.

• Corn gluten lasts 5-6 weeks. There is no carryover. After this time seeds can be planted in treated areas without being effected.

How to Use

• Application rate is 20 lbs /1000 sq ft.

• Timing is critical!! Apply in early spring, 3-5 weeks before weeds sprout (when crocus and early daffodils bloom). And in early fall when temp turns cooler. Apply in gardens any time.

• Spread around bedding plants, transplants, flowers or shrubs and rake in lightly.

• Spread evenly on lawns. Avoid any bare spots where reseeding grass.

• Sprinkle on cracks in driveways and sidewalks.

• Water in if there is no rain.

• Then allow area to dry for 2-3 days. Plants need dryness for corn gluten to effectively kill emerging weeds. If excessive rains occur, reapplication may be needed.

Is Genetically Modified (GMO) corn used to make corn gluten?

Up to 60% of the commercial corn and soybeans in the United States is grown from GMO Seed. Corn gluten sold as a preemergent herbicide may indeed contain GMO corn, but it has not yet been tested. Here's the twist. Corn gluten can reduce the need for traditional herbicides that have environmental side effects. It likely now contains GMO corn. It could be produced from non-GMO corn, but would likely be more expensive.

If GMO corn is used, can certified organic growers use it and will European markets allow it? How do home gardeners feel? And if plants are grown in soil treated with GMO corn gluten, could a crop pick up anything that show a positive GMO detect in testing?

Will the 10% nitrogen of corn gluten be a problem for low nitrogen needing plants?

Beans, peas and other legumes have reduced yields if given too much nitrogen. Also lean-loving flowers such as butterflyweed or coneflowers may not like the extra nitrogen?