Does Cornmeal Kill Weeds?

One of the most frustrating things about owning a home is when it seems like there’s always something that needs repairs or maintenance. Weeds sprouting in your garden is one such frustration. Luckily, problems like these can be solved without having to call professionals every time – and often times all it takes is one tool you probably already own!

If you are trying to kill weeds in your lawn or garden, you may have heard from a neighbor or read online that cornmeal is an effective option. But, does cornmeal actually work to kill weeds? And, if so, how does it do it? This article will discuss how cornmeal works as a weed prevention method, including how it works and the risks involved, and whether it should be used on your property.

What is Cornmeal?

If you’re looking for an organic way to kill weeds in your lawn or garden, then cornmeal might just be the answer! Cornmeal is cheap and easy to find, and you might have been told it is a great all-natural alternative to chemical herbicides.

Cornmeal is a coarse flour ground and derived from dried corn. It is consumed all over the world as a common staple food, and can be used to make dishes like corn tortillas and other dough-based products, polenta, and even porridge and grits.

However, cornmeal is NOT a product that can be used to kill weeds or prevent them from growing. If you use cornmeal in your garden, you will be disappointed with the results and will have just wasted a perfectly good food source.

Instead, what you want to use to reduce weed growth in your garden is called Corn Gluten Meal. While this is a similar product to cornmeal, it is unique from it and it has different properties that allow it to function as a weed killer. So, before we go any further, what is Corn Gluten Meal?

What is Corn Gluten Meal?

Corn Gluten Meal is a byproduct in the milling process for making corn flour. It consists primarily of finely milled de-germed protein obtained as a result of washing away starch during production. The protein content ranges from about 20% to 80%.

Corn Gluten Meal is the principal protein found inside a kernel of corn. It is commonly used to feed livestock in a mixture containing around 65% crude protein. It can be consumed by animals as well as a source of protein, energy, and pigmentation for livestock. It’s also used in pet foods to enhance digestibility.

Although the word gluten is in the name, Corn Gluten Meal does not have any true gluten, meaning it is gluten-free and can be handled by people with allergies or Coeliac’s disease.

Can Corn Gluten Meal Kill Weeds?

The short answer is that yes, Corn Gluten Meal can somewhat limit weed production in your lawn or garden. It was patented for use as an herbicide in 1991, although it is not regulated in the U.S.

Corn Gluten Meal does not work to kill pre-existing weeds that have already sprouted. For such cases, you should turn either to natural weed killers such as this Doctor Kirchner Natural Weed & Grass Killer.

There are also other home remedy options like a vinegar solution or pouring boiling water on the weeds.

What Corn Gluten Meal can do, however, is stop weeds from growing in the first place.

How And When To Use Corn Gluten Meal

To use Corn Gluten Meal as a method for weed control, there are a few steps that you should take. First, sprinkle dry corn gluten meal around the areas that weeds have grown before or are likely to grow.

Be sure to not exceed 20 pounds of CGM per 1,000 square feet of lawn, but you also need to lay down the corn gluten meal in a thick enough layer that it covers the areas fully.

When you have laid out all of the dry CGM, then simply water it lightly to activate the oils within it. You can do this method a few times, each time waiting multiple weeks for it to take effect before trying again.

How Does It Work?

Corn Gluten Meal works as a pre-emergent weed killer primarily due to its high nitrogen content. As the meal breaks down over time, it releases this nitrogen into the soil, providing a natural fertilizer for healthy lawn grasses and plants.

These grasses and plants then have a head start to out-grow the weeds that are scattered around them, and they are able to out-compete the weeds for sunlight and water if they grow faster.

The weed then wither and die out with no way to get the nutrients they need. A healthy lawn is the best deterrent against weeds growing in it.

When you spread the Corn Gluten Meal out over the weeds, it also acts as a mulch that blocks sunlight from reaching down into the soil and getting to the seeds. Mulch is another effective way at stopping weeds from germinating, and CGM acts as such when it is spread in an unbroken layer across any potential weedy areas in your lawn.

Are There Any Negative Side Effects?

Excess use of Corn Gluten Meal can lead to nitrogen runoff, which is when there is too much nitrogen in the soil and it therefore leaches into rivers and watershed runoff points. This can lead to excessive nitrogen in nearby bodies of water, which has negative environmental effects such as eutrophication of surface waters, excessive blooms of algae, hypoxia, acid rain, and even is a slight cause of climate change.

Therefore, we recommend not using too much Corn Gluten Meal when dealing with weeds, but just enough to deal with any infestations you might have. You could also mix the use of Corn Gluten Meal with other natural weed remedies, such as vinegar or boiling water.


Weeds are often a problem in the garden, but it doesn’t have to be that way. Cornmeal – or, more specifically, corn gluten meal (CGM) – can help control weeds without harming your plants. This post has covered many aspects of this topic including what corn gluten meal is, its main use in gardening, if it kills weeds or not, and any potential side effects that may be included with using this product.

Remember to use Corn Gluten Meal as a pre-emergent herbicide, and one that should be used sparingly and mixed with other organic methods of weed removal. Mostly, Corn Gluten Meal stimulates the growth of healthy lawn grasses and plants, which can then out-compete weeds for vital sunlight and nutrients.