Does Cornmeal Stop Weed Seeds From Germinating

Cornmeal is the latest natural weed killer that has been making the rounds on social media. Is it effective? Learn more. Official Blog of the UC Master Gardener Program of Contra Costa County

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.

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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.

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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.

Does Cornmeal Stop Weed Seeds From Germinating

Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County

Client’s Request: I’ve heard that I can use yellow corn meal to control weeds. Is this doable and will it hurt the soil?

Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your question about cornmeal and weeds. I am going to assume that you mean corn meal gluten (CGM), a by-product of corn starch manufacturing that is marketed to home gardeners for pre-emergent control of weeds, especially in lawns. Yellow corn meal makes great polenta, but won’t do much for weeds!

University of California research has not shown CGM to be an effective weed control strategy, but in a lawn, it may work because it is high in nitrogen and will feed the lawn, making it more dense, and likely crowding out weeds. Lawns already fed with high nitrogen fertilizers probably won’t show any significant benefit from CGM.

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CGM will have no effect on already-emerged weeds; it only suppresses some seeds’ ability to sprout. It is sometimes used though where only organic herbicides are permitted, but its effectiveness is still questionable. It should not have adverse effects on soil. Because it is high in nitrogen, it could be beneficial if your soil is deficient in that nutrient.

Better weed control can be achieved by heavily mulching the area, which will prevent weed seeds from sprouting. At this time of the year, late winter, when many of our weeds have already come up, you can try hand-pulling or hoeing out the small weeds. They are always easiest to control when they are small. This link will give you great information from UC about weed management in the landscape: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7441.html. The key to successfully reducing the weed problem in future years is to make sure none of this year’s weeds go to seed.

Weeds in our gardens are frustrating and seem to be extra-abundant this year because of all the rain we’ve had. Good luck!