Is Corn Gluten Meal an Effective Crabgrass Preventer or Simply a Very Good Fertilizer?

Over the last 20 years, corn gluten meal has been hyped as a natural “weed and feed“. Homeowners, lawn care professionals and golf course superintendents with mixed results have used it.

Weed control reports have varied from poor to excellent, and it’s finicky when it comes to environmental conditions – they have to be just right. On the other hand, if you want corn gluten meal as straight fertilizer, it’s a very good source of organic nitrogen.

Factors to Consider when Using CGM


  • Byproduct of the corn wet milling process
  • Potentially used as a natural crabgrass preventer
  • 10% nitrogen by weight – good source of slow-release nitrogen
  • Has shown to reduce weed populations by 90% when used consistently over a 3-year period – with spring and fall applications


  • To be effective as a preemergent, it needs to be applied at 20 lbs per 1000 ft2
  • Timing is important – the active ingredient dissipates in 4 to 6 weeks
  • Weed control results are inconsistent
  • 20 lbs per 1000 ft2 is a lot of product to handle and apply
  • 2 lbs of nitrogen in one application is excessive
  • Hard to find locally – you might have to purchase it on the internet and pay shipping
  • It is a lot more expensive and not as effective as synthetic weed controls

How Corn Gluten Meal Controls Weeds

CGM only works as a preemergent herbicide – preventing weed seedlings from growing into mature plants. It does not work on established weeds.

In the mid-1980s, Iowa State University researcher Nick Christians observed corn gluten meal to have pre-emergent herbicidal effects while researching pythium fungus on bentgrass greens. Further investigation found that CGM releases a protein that disrupts the root development of sprouting weed seeds leaving them vulnerable to dry conditions.

Timing and Conditions are Critical

To use CGM effectively as a preemergent you need to be familiar with the life cycle of the weed you are trying to control. Crabgrass, chickweed, dandelions, purslane, plantain, pigweed, foxtail and barnyard grass are some common lawn weeds that have been effectively controlled.

CGM needs to be applied at a rate of 20 lbs per 1000 ft2 just prior to weed seed germination. The useful window is short since the active ingredient vanishes in 4 to 6 weeks. A period of light rain or irrigation is required to activate the product and then a dry period is needed to kill the affected weed seedlings. If the soil remains moist, the seedlings will recover and the 2 lbs nitrogen per 1000 ft2 that was applied will probably cause them to thrive.

Studies have shown that you will generally see 60% control the first year, 80% the second and up to 90% control the third year. These results could be credited to the heavy nitrogen fertilizer causing the grass to grow vigorously and denying weed seedlings water, light and room to grow.

Tip: Only purchase CGM that is labeled “preemergent herbicide” or you might end up buying a corn gluten feed that is cheaper but does not work.

A Very Good Organic Fertilizer

It’s probably best to use corn gluten meal as a straight fertilizer and forget about weed control. The 20 lbs per 1000 ft2 required for weed control is equal to 2 lbs of nitrogen per 1000 ft2 – that’s a lot of nitrogen! An overdose of nitrogen for cool-season grasses in the spring. It’s really never a good idea to apply more than 1 lb of nitrogen at a time, even if it is slow release. The excess nitrogen has the potential to leach into our ground waters and will encourage fungal diseases of cool-season grasses in humid weather.

Drop the rate to 5 or 10 lbs per 1000 ft2 and you have a very nice organic fertilizer that gives lawns that nice dark green color we aim for.

Corn Gluten Hydroslate has Potential

New products have been developed that can be sprayed making them easier to handle and apply.

The new corn gluten hydrolysate products are water soluble, contain less nitrogen by weight and might be more effective than CGM for weed control – if they can be improved. CGH has been shown to be more effective than corn gluten meal in controlled environments. However, the hydrolysate form is roughly equivalent to CGM in the field and seems to be more sensitive to environmental conditions.

These hydrolysate products the have potential to be effective organic herbicides if scientists can figure out how to prevent the active ingredient from dissipating quickly.

Have you heard about the Sunday Smart Lawn Plan? It’s simple, do-it-yourself natural lawn care that’s customized to your soil, climate, and lawn.  Delivered to you right when you need it.

Sunday’s plant and soil nutrient products are made from food waste, seaweed, and molasses.  The natural additives stimulate plant growth and activate soil life.

This is Super Environmentally Friendly lawn care!

Drop the rate to 5 or 10 lbs per 1000 ft2 and you have a very nice organic fertilizer that gives lawns that nice dark green color we aim for.

More natural lawn care tips:

Organic Lawn Fertilizer | Benefits of Natural Fertilizers

Organic Lawn Fertilizer: Benefits of natural fertilizers. How natural products improve the soil and health of landscapes. Helpful DIY lawn care tips.

Chemical Fertilizers vs. Organic lawn Fertilizer

Are natural organic fertilizers safer than chemical fertilizers? Are they better or safer for lawns, the environment, and your family? Do synthetic sources of nutrients harm the soil?

Vinegar Weed Killer vs Roundup

Why your recipe for homemade vinegar weed killer won’t work. Glyphosate is a more effective and safe non-selective herbicide. Helpful DIY lawn care tips and advice. Organic weed control and more.

Find out how much your job will cost