Does Cornmeal Stop Weed Seeds From Germinating

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. Cornmeal gluten is known as a natural substitute for chemical pre-emergent herbicides. Using this cornmeal as weed killer is a great way to eradicate weeds without the threat of toxic chemicals. Learn more here. Cornmeal is the latest natural weed killer that has been making the rounds on social media. Is it effective? Learn more.

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.

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.

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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.

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?

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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.

Cornmeal As Weed Killer And Pest Control: How To Use Cornmeal Gluten In The Garden

Cornmeal gluten, commonly referred to as corn gluten meal (CGM), is the by-product of corn wet milling. It is used to feed cattle, fish, dogs, and poultry. Gluten meal is known as a natural substitute for chemical pre-emergent herbicides. Using this cornmeal as weed killer is a great way to eradicate weeds without the threat of toxic chemicals. If you have pets or small children, gluten meal is a great option.

Gluten Cornmeal as Weed Killer

Researchers at Iowa State University discovered by accident that cornmeal gluten acts as an herbicide while they were doing disease research. They saw that corn gluten meal kept grass and other seeds, such as crabgrass, dandelions, and chickweed from sprouting.

It is important to note that cornmeal gluten is only effective against seeds, not plants that are mature, and is most effective with corn gluten having at least 60% proteins in it. For annual weeds that are growing, plain cornmeal products will not kill it. These weeds include:

Perennial weeds will not be damaged either. They pop back up year after year because their roots survive under the soil over winter. Some of these include:

However, cornmeal gluten will stop the seeds that these weeds shed in the summer so that the weeds will not increase. With consistent use of gluten meal products, these weeds will gradually decline.

How to Use Cornmeal Gluten in the Garden

Many people use corn gluten on their lawns, but it can be safely and effectively used in gardens as well. Using gluten cornmeal in gardens is a great way to keep weed seeds from sprouting and will not damage existing plants, shrubs, or trees.

Be sure to follow the application instructions on the package and apply before weeds start to grow. Sometimes this can be a very tight window, but is best done in early spring. In flower and vegetable beds where seeds are sown, be sure to wait to apply at least until the seeds are grown up a bit. If applied too early, it can prevent these seeds from sprouting.

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Using Cornmeal Gluten to Kill Ants

Cornmeal gluten is also a popular method to control ants. Pouring it wherever you see ants traveling is the best option. They will pick up the gluten and take it to the nest where they will feed on it. Since the ants cannot digest this cornmeal product, they will starve to death. It may take up to a week or so before you see your ant population dwindling.

Tip: If you have large areas to cover, you can try a spray form for ease of application. Apply every four weeks, or after heavy rains, during the growing season to maintain effectiveness.

Cornmeal as Weed Killer?

The quest for the perfect weed killer has led to some interesting preparations. You’ll find natural remedies that range from using boiling water to vinegar and soap. While many of these remedies work, they tend to be difficult to implement on an entire batch of weeds. They also have only short term effects.

Cornmeal is the latest natural weed killer that has been making the rounds on social media. The prospect of being able to kill weeds with a simple sprinkle of cornmeal is exciting. Most people find cornmeal to be cheap and readily available, but the real question is does it work?

What is Cornmeal vs. Corn Gluten Meal?

The biggest mistake that most people take with this natural weed remedy is running out to buy cornmeal from the grocery store shelves. The type of cornmeal that you eat is not the same as what you need for weed killing purposes.

The cornmeal in your pantry is made from ground-up corn kernels. This is what you use as an ingredient in recipes for cornbread and other dishes.

Corn gluten meal is a byproduct that is created during the wet milling process of making cornmeal. It is not meant for humans to eat, but it is sometimes used in pets and cattle feed.

Since corn gluten meal has high levels of protein, nitrogen, and oils, it is also used for lawn fertilization and weed control purposes. It is sold in lawn and gardening stores rather than at your local grocery store.

How Do People Use Cornmeal as a Weed Killer?

Corn gluten meal is found in both pellets and powdered forms. The application process involves spreading it in a specific amount that is based upon how many square feet of ground needs to be covered.

After the meal is distributed evenly on the ground, you then need to water the lawn lightly to activate the oils. If the application does work, it is only effective for around 5 to 6 weeks. Then, the meal must be reapplied.

Does It Work on All Weeds?

This method only works on weeds that have not sprouted yet. People often use it on annual weeds such as purslane. Keep in mind that it will not work on perennial weeds that have already established a root system.

How Effective Is It?

There have been multiple studies on the use of corn gluten meal as an effective weed killer with mixed results. The primary issue with this method is the difficulty of applying it at just the right time to knock out the weed seeds.

Weeds grow throughout the year in Arizona. Even annual weeds may occasionally pop up before you expect them in the spring. Once they do, this method is not effective at all. It also requires frequent reapplications. Keeping up with this method can be frustrating for busy property owners.

What Are My Other Options for Dealing With Weed Problems?

Pre-emergent sprays work similarly to corn gluten meal by suppressing weed growth at the seed level, but it is a little different. A pre-emergent spray prevents seed germination. The seeds never develop roots or sprouts.

Even if you choose to experiment with corn gluten meal, you can still expect to need post-emergent weed spraying. This method gets rid of weeds that are already visible above the ground that the meal cannot kill.

So what’s the verdict? Corn gluten meal may help with preventing weeds from emerging from your lawn. This only works if you are diligent about following the proper application process and okay with it not always working.

There are also more effective methods for getting rid of those unsightly plants. Proper weed control involves a careful plan that addresses the types of weeds that appear in your lawn at every stage of growth.