#1 – Not Applying Corn Gluten Meal Heavy Enough

I have had many homeowners say, “your corn gluten meal application works so much better than the one I did myself.” They proceed to take me to their garage or shed and show me a small 20 pound bag of CGM that is half used and they say I applied this last year and I had tons of weeds. I tell them that the entire 20 pound bag would only cover about 1/5th of their entire lawn. That is when their eyes get big, they laugh out loud and say something like, “oh, so I didn’t use nearly enough.”

For corn gluten meal to control weeds, it needs to be applied at 20 pounds per 1000 square feet. This is a very heavy application rate, especially compared to a chemical fertilizer, which typically has an application rate of 2-3 lbs per 1000 square feet. Most broadcast spreaders are not designed to apply corn gluten meal and even at the highest setting they cannot apply at a 20 pounds per 1000 square feet rate. Therefore, multiple passes may be necessary for certain spreaders.

#2 – Applied the Corn Gluten Meal Too Late In the Season

Many homeowners make the same mistake. In late spring the man of the house looks at their lawn and notices there are a lot of yellow dandelions growing. Not liking these unwanted intruders, he yells to his wife, “Honey, I am going to go to the store and get some dandelion control.” She yells back, “Make sure it is safe for the kids and dog!” He yells back, “Of course honey!” He then hops in his car and heads to the local hardware store or nursery and picks up the only product on the shelf that says organic weed control, which is a bag of corn gluten meal. He heads back and applies the product at the 20 pounds per 1000 square foot rate and a week later there are 1000’s of dandelions!

So why didn’t the corn gluten meal work? Simple, if you are already seeing dandelions growing in the lawn, then it is too late for corn gluten meal!

Corn gluten meal is a pre-emergent weed control and fertilizer, which means it needs to be applied prior to the weeds germinating. In Colorado, depending on the weather, the majority of the dandelions start to germinate around April 15th and the peak dandelion season is around May 1st.

Dandelion

As long as there isn’t snow on the ground we recommend applying corn gluten meal as soon as March 1st and we continue to apply the product up to April 10th. The earlier in the season that we corn gluten meal is applied, the better it will control weeds!

#3 – There are Two Types of Corn Gluten Meal

There are two types of corn gluten meal? Yes, and most organic gardening experts don’t even know this fact. There is a more expensive corn gluten meal that is 60% protein and there is a less expensive corn gluten meal that is 20% protein, yet they have the exact same name. There is a huge price difference between the two different types of corn gluten meal products. Some manufacturers will use the much less expensive 20% CGM or mix in a 50%/50% blend to save money, but the results will be vastly different.

A 60% protein corn gluten meal product will control weeds when applied at a 20 pounds per 1000 square feet rate. Yet the 20% protein corn gluten meal will only control weeds if applied at 60 pounds per 1000 square feet. Unfortunately, there is no way to tell from an ingredient list if the corn gluten meal used in a product is 20% protein or 60% protein.

#4– Corn Gluten Meal Will Only Prevents Weed Seeds from Germinating

Corn gluten meal only prevents weed seeds from germinating properly and it will not prevent weeds that are germinating from an existing root system from germinating.

First, we need to explain what the difference is between annual weeds, perennial weeds and biennial weeds.

Annual weeds have a 1-year life cycle. They germinate from a seed, emerge, they produce a flower stalk, flowers, set seeds (usually a lot of seeds), mature, and then dies. Examples of annual weeds include: Chickweed, Hairy Bittercress, Yellow Oxalis, Lambs Quarters.

Biennial weeds have a 2-year life cycle. They germinate from a seed, emerge usually form a rosette radial cluster of leaves close to the ground, in the first year. The second year, the plant produces a flower stalk, flowers, sets seed, matures, then dies. Examples of biennial weeds include: Bull Thistle and Common Mullein.

Perennial weeds live longer than 2 years. They germinate from seed, emerge, and may or may not develop a flower the first year. Then the plant will die back every autumn and winter, and then return in the spring from their existing root system or rootstock. Examples of perennial weeds include: Bindweed, Dandelion, Canada Thistle, and Plantain.

Since corn gluten meal prevents weed seeds from germinating properly there will only be control on annual weeds, and biennial and perennial weeds that are germinating from seed. Therefore, the second year of biennial weeds and established perennial weeds will not be controlled with corn gluten meal.

Instead of giving a long explanation about weed seeds, second year root systems, perennial weeds, etc. We find it is much easier to understand what percentage of weed control to expect if corn gluten meal is properly applied both spring and fall every year.

Year 1: 60% control rate on weeds

Year 2: 70% control rate on weeds

Year 3: 80% control rate on weeds

Year 4: 90% control rate on weeds

Year 5+: 90%+ control rate on weeds

Corn gluten meal is a very effective tool in organic lawn care, but it has its limitations. If you are thinking that one application of corn gluten meal will kill all your weeds in your lawn, then you will be very disappointed with the results that it will produce. If used regularly over a 4 year time span, corn gluten meal is a wonderful 100% natural pre-emergent weed control and fertilizer that will control weeds in a lawn.

Hopefully these tips will make your corn gluten meal application work! After all, the reason we want to use a natural weed control vs a chemical weed control is because we care more about our kids and pets than we do about a perfect lawn!