Weed Seed Inhibitor

Corn gluten meal is sold as an organic pre-emergent weed control alternative to synthetic chemicals. Success relies on timing. Want to kill weeds before they start? Try our Pre-emergent Weed Control lawn treatment Corn gluten meal is the new herbicide for lawns. It prevents weed seed from germinating giving you a weed free lawn. Find out how to apply it and how well it works. Which weeds are controlled? Is it good for crab grass? This is not corn meal and not all corn gluten meals are effective.

Corn Gluten: An Organic Pre-Emergent Herbicide

Kelly Burke is a professional turf manager for a manicured corporate campus in New England. He is accredited in organic land care and is a licensed pesticide applicator. He formerly managed the turfgrass as a golf course superintendent and has held several senior management positions at private country clubs overseeing high maintenance lawns.

Kathleen Miller is a highly-regarded Master Gardener and Horticulturist who shares her knowledge of sustainable living, organic gardening, farming, and landscape design. She founded Gaia’s Farm and Gardens, a working sustainable permaculture farm, and writes for Gaia Grows, a local newspaper column. She has over 30 years of experience in gardening and sustainable farming.

Emily Estep is a plant biologist and fact-checker focused on environmental sciences. She received a Bachelor of Arts in Journalism and a Master of Science in Plant Biology from Ohio University. Emily has been a proofreader and editor at a variety of online media outlets over the past decade.

Corn gluten meal is a powdery byproduct of the corn milling process. Originally used as a supplement in hog feed, corn gluten has become a common organic alternative to synthetic chemical herbicides. It can be effective as a pre-emergent herbicide used to control crabgrass and other lawn weeds, and it also has nutritional properties. Corn gluten meal is about 10 percent nitrogen by weight, meaning 100 pounds of corn gluten contains 10 pounds of nitrogen. This organic source of nitrogen is slowly released over a three- to four-month period.

How Corn Gluten Works

Corn gluten does not prevent weed seeds from germinating, but it does inhibit those seeds from forming roots after germination. This means that applications must be very carefully timed. When the application of corn gluten is timed correctly, crabgrass seeds germinating will form shoots but not roots, and will therefore die, provided there is a short dry period after seed germination. However, if conditions are too wet immediately after seed germination, the weed can recover and establish a root.

Application Timing

Corn gluten is useful only as a pre-emergent herbicide; it provides no post-emergent weed control. If crabgrass and other weed seeds have already germinated and taken root, a late application of corn gluten will only serve as fertilizer for the weeds. Further, applications of corn gluten need to be precisely timed around rainfall or watering. After application, corn gluten needs to be watered in, either by rainfall or by artificial watering, within five days of application. Rainfall of about 1/4 inch, or a comparable artificial watering, is ideal. After this, a dry period of one or two days is required to prevent weed seedlings that have germinated from growing roots.

In other words, corn gluten needs water just after application, but a dry period is then required in order for germinated weed seeds to have their root production inhibited. It can be quite difficult to get this application timing precisely correct.

The first application of corn gluten won’t suppress all of the weed seeds, and a single application may help suppress weeds for four to six weeks. Heavy soils, extended rainy weather, and hot spells may require a monthly application or a second application in late summer. The initial results may be disappointing but after several applications, corn gluten sometimes reaches 80 percent effectiveness at controlling crabgrass.

How Much Is Needed?

Application rates vary by form: powder, pelletized or granulated. The standard application rate is 20 pounds of corn gluten per 1,000 square feet of lawn. This rate also provides about 2 pounds of nitrogen per 1,000 square feet.

The effects of corn gluten are cumulative, meaning that the results improve with repeated use over time.

The Downside

Some experts are critical of using corn gluten as a pre-emergent crab-grass killer, pointing to several points:

  • Corn gluten is costlier than conventional pre-emergent herbicides. Because multiple applications are often required, you could be handling hundreds or even thousands of pounds of the product, depending on the size of the yard. Sprayable, liquid forms of corn gluten can make applications easier, but they are still costly.
  • Timing is critical for both organic and synthetic chemical pre-emergents. It’s very important to remember that all pre-emergents, including corn gluten, will suppress all seeds, including grass and flower seeds. If you are using non-selective pre-emergents in the spring and summer, any lawn seeding should be done in the fall.

Definition

A synthetic chemical pre-emergent is a non-organic herbicide that is applied to the landscape prior to weeds and other unwanted plants growing. In essence, it prevents those plants from emerging from the soil where seeds might lie.

  • The nitrogen in corn gluten has drawbacks. Some turf specialists argue that extra nitrogen only gives weeds the advantage.
  • Encouraging new grass is more effective. Crabgrass is a filler weed that thrives in bare spots or areas with thin turf grass, and organic turf specialists contend that seeding with new grass is just as effective as applying pre-emergent herbicides such as corn gluten. Dense, healthy turf will naturally crowd out crabgrass, so growing more grass and filling in those thin areas and bare patches may be a better solution.
See also  Scotts Fall Weed And Feed Seeding

Bottom Line

Corn gluten does work as a pre-emergent herbicide, through a mechanism that inhibits germinated weed seeds from establishing roots. But timing the applications correctly is tricky, and it may require repeated applications in order to really see the desired results. Further, corn gluten can also inhibit new turf grass seeds from becoming established.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Inhibitor 18-0-6 Pre-emergent Weed Control

Weeds can distract from your lawn’s appeal and deprive grass of nutrients and water needed to thrive. That’s why Natural Alternative® offers pre-emergent weed control lawn treatment to help fight off pesky weed invaders before they become a nuisance. Natural Alternative® Inhibitor 18-0-6 Pre-emergent Weed Control fights all types of weeds and can be spread directly onto established turf to help prevent crabgrass and other annual weeds.

We’ve got you covered

Our Inhibitor can be used on a variety of grass types, including all Natural Alternative® seed selections. Inhibitor’s pre-emergent lawn treatment also includes a mix of nitrogen and potassium to help your lawn thrive while preventing weed emergence. Our Inhibitor offers control against annual grass weeds like crabgrass, goosegrass, foxtails and more. It’s time to enjoy your outdoor space without being burdened by invaders sprouting up in your lawn.

Summer Lawn Weeds

Product Information

info Application Instructions arrow_drop_down_circle

When to Apply

Successful pre-emergence control of the annual grass weeds listed on this label requires proper timing of application. Apply this product 1 to 2 weeks prior to the germination of annual grass weeds. If application timing does not coincide with the normal germination period of any of the annual grass weeds listed on this label, weed control results may be erratic or poor. Weed seeds typically begin to germinate when soil temperatures reach 55 degrees Fahrenheit (3 to 5 days of 60-65 degree weather can change your soil temps). Typically applied mid-march in most areas, gauging your weather is the best practice when applying pre-emergents. Remember if you can see the weed, pre-emergent controls will not help. Apply before a light rain or lightly water the product in.

Application Rates:

Apply 3 to 4 lbs. per 1,000 sq.ft. – If you have an issue with weeds, we recommend 4 lbs. per 1,000 sq.ft. as a treatment and 3 lbs. per 1,000 sq. ft. as a preventative.

Things to remember when controlling weeds:

  • Anytime you treat for weeds it is important to make sure you overseed the lawn or the area the following season.
  • Weeds love weak spots in the lawn, if you are treating weeds in an area that is already weak and your remove more weeds you are creating the perfect spot for more weeds. To keep a healthy, thick and growing lawn it takes work especially in the beginning. Control your weeds, continue to fertilizer through each season and overseed when it is best for your area for best lawn results. Once your lawn is doing better after all of your hard work, weed controls aren’t always necessary so you can focus on fertilizing at least 3 times a year (we recommend 5 application) and spot seeding in any areas that may need it after possible seasonal damage (seeding in Fall is best, spring if needed).

Don’t use Inhibitor on newly seeded lawns. You can seed the following season (Control in the spring, seed in the fall).

Weeds controlled when applied prior to weed germination:

Annual Grasses controlled: when applied prior to weed germination

  • Annual Bluegrass
  • Barnyardgrass
  • Crabgrass (large, smooth)
  • Goosegrass
  • Crawfootgrass
  • Foxtails

In areas where germination of the annual weed grass species continues for an extended period of time, make a second application at the recommended rate 8 to 10 weeks after the first application on cool season turfgrass and 10 to 12 weeks after the first application on warm season turfgrass.

General Use Precautions and Restrictions:

  • Do not apply this product to golf course putting greens.
  • Do not apply this product through any type of irrigation system.
  • Any cultural practices that disturb the soil, such as aeration or verticutting, should be done prior to application of this product.
  • Do not apply to overseeded turf within 60 days after seeding or until after the second mowing.

Specific Use Restrictions:

  • Do not make more than 2 applications totalling 11 pounds of this product per year on turfgrass.
  • Maximum single application rate: 8 pounds per 1,000 square feet.
  • Minimum Re-treatment Interval: Cool season turf – 56 to 70 days; warm season turf – 70 to 84 days.

Download our spreader settings sheet to find proper settings for your spreader.

Corn Gluten Meal – Does it Work For Weeds?

Corn gluten meal is the new herbicide for lawns. The movement away from synthetic chemical herbicides has left a gap for managing lawns and researchers are scrambling to find an organic solution. One product that is showing promise is corn gluten meal. Its proponents claim that it prevents weed seed from germinating, and if seeds don’t germinate you have a weed free lawn. Sounds like a perfect solution.

See also  Homegrown Weed Seeds

There are scientific reports, both for and against the product. Anecdotal evidence from gardeners is also mixed. Does the product work? How should it be used? Are people using it correctly?

lawn and corn gluten meal

What is Corn Gluten Meal?

In the 1990s, Dr. Nick Christians at Iowa State University was doing some work on golf putting greens and stumbled upon the herbicidal qualities of a product called corn gluten meal. This natural material is a by-product of the wet milling process used to produce corn starch and corn syrup from corn.

Corn gluten meal is 60% protein and contains 10% nitrogen, by weight.

Corn gluten meal is not the corn meal found in grocery stores, as so many sites on social media claim. Corn meal has no herbicidal properties and as far as I can tell the only thing it will do in the garden is feed ants and slugs.

Not All Corn Gluten Meal is The Same

There are different qualities of corn gluten meal and the one that is a herbicide contains 60% protein. This product is always labeled as a pre-emergent herbicide.

The true corn gluten meal herbicide is expensive and so many people have tried a cheaper product called corn gluten feed, or distillers grain. These animal feed products may even be called corn gluten meal but they will not be labeled as a pre-emergent herbicide.

One reason corn gluten meal may be getting bad press is that gardeners are trying to use the feed products and then reporting they don’t work. They don’t work because they don’t have a high enough protein level – they are the wrong product.

Another common problem is that corn gluten meal needs to be applied at a heavy rate of 20 pounds per 1,000 sq ft and most home spreaders can’t reach this level. If it is not applied thick enough, it won’t be effective.

Does it Prevent Seeds From Germinating?

Many sites report that corn gluten meal prevents seeds from germinating, but this is a myth.

After treatment with corn gluten meal, seeds will germinate normally, by producing a radicle (aka root). The food for growing the radicle comes from inside the seed and is unaffected by its new environment. Once the radicle is formed it starts to make roots which absorb water and nutrients from the soil. Corn gluten meal inhibits the formation of roots – it does not prevent seed germination.

The death of the seedling depends on a perfect storm of events. The developing roots need to absorb enough protein from the corn gluten meal to have an effect. This is why higher application rates generally result in higher weed control. The roots also need to be on the dry side after germination. Too much water dilutes the effect of the protein and roots keep growing. As discussed below, application of the product is critical.

If corn gluten meal stops root growth, why does it not affect mature plants?

Mature plants have many more roots and they have roots that are located deeper in the soil. They are never exposed to enough protein to have a significant effect. Corn gluten meal does not harm existing plants, even if they are weeds.

Corn Gluten Meal – Does it Work?

Dr. Nick Christians’ original field work showed that c orn gluten meal applied at 99, 198, 297, 396, 495, and 594 g/m2 reduced crab grass infestation by 50, 65, 80, 95, and 93%, respectively when applied 1 week before crab grass germination. Applying it 4 weeks before germination required higher amounts to have the same effect.

When 22 different weeds were tested they found that all were reduced, but the degree of reduction varied by both species and application rate. At low rates some weeds were unaffected. Since this work was done, other research has identified a few weeds that seem to be immune to corn gluten meal.

Most discussions refer to weeds, but non-weed seeds like grass, perennials and vegetables are also affected.

Others have also tested corn gluten meal. A study out of Oregon State University says that they could not replicate the initial field findings. I am not sure that this work was ever published? The work was part of a Masters degree and is available as a Thesis. It found that corn gluten meal did not reduce the number of weeds. In it’s conclusion it states that this could be due to the fact that the testing was done on clear soil, with no grass and therefore no competition, or that it might be due to an old product. The product was not tested in the lab to verify it worked. The work did not record rain fall during the tests and Oregon can be quite wet, so it is also possible that excess rain kept the product from working.

The University of Guelph Turf Grass Institute has researched corn gluten meal and concluded that the product does control weed seed germination but that it was not 100% effective.

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Dave Gardner from Ohio State University made a video showing his results. He found that to be effective you needed to use twice the recommended amount of 20 lbs/1,000 sqft, which makes application very expensive. He also commented that you need to apply it for at least two years since “first year results are disappointing.”

You can find both positive and negative research for this product. The key might well be in using good quality product and using it correctly. Any research that does not provide rain data is not of much help since a dry period after application is required for the product to work.

Too Much Nitrogen

Corn gluten meal contains about 10% nitrogen by weight in an organic form, mostly protein. The nitrogen is slowly released into the soil as it decomposes over a 3-4 month period.

This is an important fact since this nitrogen makes both turf grass and existing weeds grow better. It is actually a good, but expensive, lawn fertilizer.

Any weed seed that is not stopped, will be able to use the extra nitrogen to grow faster than if would in an untreated lawn. This can be a big problem if you apply it at the wrong time.

This points out one of the serious limitations of anecdotal reports. Almost none of these count actual weeds, so it is quite possible that people conclude the product did not work because it produced nice large weeds which cover a large area of the grass. The overall appearance of weeds was not reduced.

Is It Safe for Grass?

Corn gluten meal will not harm any existing type of lawn grass or other perennials. It should not be used at the same time as seeding a new lawn.

When and How Should It Be Applied?

Corn gluten meal needs to be applied just before weed seeds start to germinate. Most weed seed germinates in spring, with a second flush happening in fall. For crab grass control, it is recommended that you apply it when the forsythias start to bloom.

There are two problems with this advice; different weed species germinate at different times and germination is affected by the environmental conditions, which change from year to year. So it is tricky to apply it at the right time. Apply too late and the nitrogen feeds the already germinated seed. Apply too early and it has limited effect.

A rate of 20 pounds per 1,000 sq ft reduced crab grass by 60%. Higher rates should be more effective, but they will also cost much more. You can get 90% control, but the cost does not warrant the results.

Water it in right after application.

The next step is critical. It must remain dry for 7 days after it is applied. If you get too much rain, the excess water will reduce the herbicidal qualities of the product and you will see no weed reduction. How well do you trust the weatherperson?

Corn gluten meal will remain effective in soil for up to 6 weeks provided that it stays dry enough to prevent microbes from decomposing it.

More Corn Gluten Meal Myths

Alters pH

Corn gluten meal will not alter the pH of the soil to any significant amount.

Effective on All Weed Seed

It is effective on most types of seed, but not all.

Works by Drying the Seedlings

Many sites make the incorrect claim that corn gluten meal dries out the seedling. This is not correct. It has been shown that Alaninyl-alanine and 4 other dipeptides cause roots to stop their development.

Can be Used All Summer

Ads for product and some gardening sites recommend that the product can be used all summer long. It is true that it can be used all summer long, but few weed seeds germinate in summer. Using the product in summer, unless you are trying to get rid of summer germinating weeds, is a waste of money.

It Is Natural and Safe

Since this is a natural product everyone assumes it can be used without risk, but that is not quite true. Corn and corn by-products such as this are known to cause allergies in some people and this condition can be serious. If you or your family suffer from respiratory or hypersensitivity due to corn, avoid exposure to corn gluten meal.

Should You Use Corn Gluten Meal?

The product works but is not 100% effective. It must be used correctly or it won’t work. If you are located in an area which is particularly wet in spring, it is probably not going to work.

If your lawn has a lot of existing perennial weeds, the nitrogen in corn gluten meal will make them grow better and make the lawn worse. Deal with the perennial weeds first.

Corn gluten meal has become very expensive and to be effective it needs to be applied thickly. If you do use it, don’t skimp on the application.

This is a good product to try if you have a lot of crab grass (it is an annual), live in an area with a dry spring and you are not allowed to use, or don’t want to use synthetic herbicides.