An experiment starts: corn gluten

Yesterday I posted about a lawn care task, specifically applying corn gluten as a pre-emergent herbicide. It's organic, safe, prevents weeds from growing, smells like corn-based snacks -- what more could a gardener ask for? Well, maybe that it actually works. You see, it was pointed out in the comments that another study was done, and its results questioned the utility of corn gluten as a pre-emergent. In fact, that study concluded that it had no herbicidal properties at all.

Although it's difficult or impossible for most of us to duplicate those studies that universities do -- we have everything except the time, experience, equipment, manpower, and funding -- in this case I think I can do a simple test to satisfy my own curiosity. So today I'm starting an experiment to see if the corn gluten works for me.


With a little bit of a background in experimental science, I know that there are too many variables here for me to control, and I won't be duplicating the conditions found in the garden. So I'll never be able to say that the corn gluten always works, or always doesn't. I should be able to tell something though, so I'm going ahead with my simple experiment.

I'm starting with some fresh seed starting mix:

Then I'm adding a liberal amount of grass seed:

This is seed from last fall that my neighbor donated specifically for the test although he did not know it. I asked for a tablespoon of seed and got at least a cup of it, so there's plenty to redo the test if something goes wrong.

I just spread it over the surface of the "soil", trying to get the coverage as even as I could:

Then I put down the corn gluten over half of the area:

Yes, I'd like to order a 12" deep dish, half corn gluten, half cheese please.

Then watered well using my spray bottle, and covered with a thin sheet of plexiglass:

I'll keep the grass seed moist by spraying it a couple of times a day if needed, and hopefully will see some green in a few days. How long does it take for grass seed to germinate? It's been several years since I've seeded my lawn...

What I hope to see is that the corn-free side germinates fully, while the side that's been glutenized will be free of any grass blades, or will have noticeably fewer plants.

I've already thought of a problem though. Grass seed may germinate too quickly, and the corn gluten may not have had enough time to break down and release it's inhibitors. So if I see the grass germinate equally on both sides I'll have to redo the test, adding the corn gluten to the soil a week or so before adding the grass seeds.

I'll be reporting on this in a few days, or however long it takes the grass seed to germinate. I hope it doesn't take too long -- I'm running out of room on my seed starting table and I haven't even really started any veggie seeds yet!

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anne  – (March 3, 2011 at 8:11 AM)  

looking forward to seeing how your pizza experiment works, or the next pizza if necessary....speaking of veggie seeds, I bought my shelling & sugar snap pea packets the other day so I am ready for when the snow goes and the ground warms up later this month!

Gerhard Bock (Succulents and More)  – (March 3, 2011 at 9:42 AM)  

I'm very curious to see what happens. I'm rooting for the corn gluten. We need more organic products that work.

Alice Joyce  – (March 3, 2011 at 10:31 AM)  

I'll look forward to seeing how this experiment plays out... Organic is always best!
Good to have found you on Blotanical, a great place to connect.
aka Bay Area Tendrils

Masha  – (March 3, 2011 at 11:14 AM)  

Interesting. I hope it works for you, I am looking forward to finding out the results. I love a challenge. Good luck.

Susan in the Pink Hat  – (March 3, 2011 at 2:54 PM)  

Good for you doing a small scale experiment. I'm a bit weary with a sample size of one, but, it's good to do a test anyway.

Alan  – (March 3, 2011 at 4:38 PM)  

Thanks for all the comments!

Susan: I agree, but gotta start somewhere. I expect to be repeating these tests for a few months. It will be easier once I can set some trays up outside.

Toni - Signature Gardens  – (March 3, 2011 at 5:30 PM)  

The latest recommendation by Texas A&M Extension Specialists is to put CGM down at the rate of 80 pounds per 1000 sq ft 3 times at 2 week intervals (3 times over 5-week period). They did four squares. One was left blank, one got one application, next square got 2 applications, next square got 3 applications. The single application brought an 88% reduction in weeds. The 3-time application achieved a 94% reduction in grassy weeds and 99% reduction in broadleaf weeds. 80 lbs/1000 is a pretty heavy application.

Alan  – (March 3, 2011 at 5:53 PM)  

80 lbs/1000 is VERY heavy! The bag I have is 25 lb and it says it covers 1500. I'm glad to see that they saw positive results though.

Based on the cost of this stuff, and the fact that 2 more applications gets you only a 10% increase in effectiveness, I think I'd stick with a single application, even though I've put it down at 1/4 strength according to their results.

Anonymous –   – (March 3, 2011 at 9:21 PM)  

I too am interested how your test plays out. I am off to see what Cornell has on this as a study. Like Texas A&M I am betting they have similar results if they did indeed do a study.

Andrea  – (March 3, 2011 at 10:57 PM)  

Hahaha, i am new here, thanks to your pick for my post yesterday. This little experiment excites me too, haven't heard of gluten as herbicidal. I think you are right with your presumption, is it maybe better if the gluten is soaked in water first before putting there? But still i will follow your results. BTW, i love the photos with great DOF.

ricki 'sprig to twig'  – (March 5, 2011 at 4:40 PM)  

I have been experimenting with the stuff for a while now. When I scoop up mole hill dirt (the little guys make it light and fluffy) I mix in about 2 shovels worth of corn gluten meal and use it to build up berms. Works pretty well, and avoids that icky yellow-orange color and the moldy stage it goes through when used alone. Glad to have found you on the title of your blog.

Nat  – (March 9, 2011 at 7:24 PM)  

This is an interesting study. I work at a greenhouse that has serious weed problems and I've been trying to brainstorm a way to manage the weeds. Roundup is kind of an awful practice, but what other options do you have when you have a 20+ greenhouse property, pulling them by hand is impossible. Wish there was a solution... Nice post!

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