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Corn Gluten Meal as Weed Control?: 20 Years Later, the Jury is Still Out

Corn gluten meal is a great fertilizer, but its value as a weed control is marginal.

Corn gluten meal is a great fertilizer, but its value as a weed control is marginal.

Scarcely any subject in organic lawn care has spurred more discussion in the past two decades than corn gluten meal, the corn bi-product that was patented by Iowa State University in 1991 for its pre-emergent weed control properties. In the past decade, as the demand for alternatives to toxic chemicals has risen, the use of corn gluten meal on lawns has grown exponentially. In many cases, though, so has the frustration of consumers who expect the corn gluten meal to work as efficiently as its chemical counterparts.

My standing answer to anyone who asks about this natural weed alternative is that corn gluten meal has been vastly oversold by an overeager industry. With the rising prices of corn gluten meal in the past three years, homeowners can go broke trying to buy enough product to really make a difference in their weed population.

That does not mean, however, that the product has no value in lawn care or gardening . . .

SOME BACKGROUND

Dr. Nick Christians, one of the most widely respected figures in the lawn care industry, is credited with developing corn gluten meal as a pre-emergent lawn herbicide. His product kills the dicot weeds (clover, plantain, dandelions etc.) before they grow to adult size. The weed seeds actually do germinate, but the corn gluten meal inhibits the expansion of the plants’ roots and they quickly die of dehydration. So far, so good.

Iowa State’s own research on the subject, however, shows that to achieve anything close to full control requires the application of at least 20 pounds of corn gluten meal per 1,000 square feet — at exactly the right time in the spring — just before the weed seeds germinate. Corn gluten meal doesn’t inhibit weeds that already have root systems; in fact it makes fully formed weeds grown even faster due to the nitrogen content of the product.

MORE ABOUT TIMING

One of my pet peeves about the overselling of corn gluten meal is that the companies market the product as a pre-emergent control 52 weeks a year. And while they’re technically not lying, any gardener knows that the majority of weed seeds — especially the dreaded crabgrass seeds — germinate during a very short window in late winter and early spring depending on the climate. The general rule of thumb is to apply the corn gluten just as the forsythia plants break into bloom in the North, or the dogwoods begin to bloom in the South.

If you apply corn gluten meal anytime before or after that window, the product’s efficacy for weed control falls through the floor. The unsuspecting consumer can get ridiculously frustrated by unfulfilled expectations . . . especially given the price.

THE COST

For a long time, corn gluten meal was a good deal. Given the volatility of the commodity markets that began in 2007, however, the price has at least quadrupled in the past three years. A quick Google search today reveals just how out of whack the market has become: High Country Gardens sells a 7-pound bag for $21.95: http://www.highcountrygardens.com/catalog/product/H0033/; Amazon is offering a 25-pound bag of Espoma Organic Traditions for $30.95. That’s a better deal per pound. But when you need to apply 20 pounds per 1,000 square feet to achieve decent weed control, you’re still looking at hundreds of dollars of cost for an average 8,000-10,000 square foot American lawn.

That cost factor drives the organic lawn care industry crazy. The companies who rely on corn gluten meal for their weed control can’t possibly compete on price with the chemical industry, which dumps its poisons onto people’s lawns at pennies to the dollar compared to corn gluten meal.

CORN GLUTEN MEAL’S UPSIDE

Having said all of that, I am not completely anti-corn gluten meal. I was impressed by the tactic of one of our former sponsors, Bradfield Organics, which began selling corn gluten meal as a straight fertilizer in 2007 — while not making any claims about the product’s ability to control weeds. In my lawn trials for my book here in Maine, I found corn gluten meal to be an amazing grass fertilizer — which makes sense if you think about it because corn and grass are from the same plant family. Corn gluten meal gives the lawn a nice, natural dark green hue and, at least anecdotally from many folks in the organic lawn industry, seems to provide a large measure of disease resistance.

So, as a once-a-year fertilizer — if you can afford it — on your lawn, it’s a hell of a product. And if you’re just using it as a fertilizer, you can drop the rate to 10 pounds per 1,000 square feet and still get substantial value. Corn gluten meal contains 10 percent nitrogen by weight, so at 10 pounds per thousand, you’re putting down a pound of nitrogen. That, in combination with recycling your grass clippings back into the lawn and allowing 5-10 percent clover to grow in the lawn, will give you more than enough nitrogen for your lawn for the entire season. AND if you happen to apply that 10 pounds per thousand right now in the north, just as the forsythia are about to bloom, you will get some weed control. Just don’t set your expectations too high.

SO WHAT ABOUT WEED CONTROL?

I wrote a whole chapter in my book about weed control that had very little about corn gluten meal, for all the reasons stated above. If your lawn is mostly weeds, it’s because your soil wants to grow weeds and not grass. The sustainable way to manage weeds on the lawn is to change the soil conditions so the soil wants to grow grass. We review this at length in our book and in the how-to videos at http://www.safelawns.org/video.cfm. Other weed control factors include: 1) mowing height, the taller the grass, the fewer the weeds; 2) avoiding raking in spring so weed seeds don’t get stirred up and germinate; 3) overseeding whenever thin or bare spots appear on the lawn; 4) pulling or spot spraying weeds with organic herbicides when necessary. We also have high hopes for the new iron-based selective herbicide, which is now available from our sponsor, GardensAlive: http://www.gardensalive.com/product.asp?pn=3721.

ONE LAST NOTE

Several companies are selling liquid corn gluten as a weed control product. Iowa State University’s research indicates that this liquid hydrolosate does have slightly better weed control efficacy than the granular or pelletized corn gluten meal, but the same cost and timing issues stated above still apply. In other words, buy it with your eyes open.

About The Author

Paul Tukey

An international leader of the green movement, Mr. Tukey is a journalist, author, filmmaker, TV host, activist and award-winning public speaker, who is widely recognized as North America's leading advocate for landscape sustainability and toxic pesticide reduction strategies.

Number of Entries : 1023
  • Joe Johnson

    THANK YOU! Finally someone publishes the truth about corn gluten. I’ve long thought this product was ridiculously misleading, or at least the marketing was.

  • http://www.firebellylawncare.com Tom Kelly

    Hey Paul,
    I also wrote an article about the upside and downside about corn gluten on our blog.

    http://firebellylawncare.com/blog/

    Our company is offering the newly formulated liquid version of CGM this year and are expecting it to be pretty successful. My biggest issue with the granular corn gluten was the fact that it was providing an incredible amount of N to the lawn especially when folks were using it twice per year like some professionals were suggesting. It created an incredible contradiction in terms of stopping weeds from growing while feeding them gratuitously.

    I think that the hydrolysate version will be much more effective because it removes the N from the treatment. If anybody is interested they can get more information here:

    http://www.firebellylawncare.com/product.php?item=17

    Tom Kelly

    • Paul Tukey

      The liquid corn gluten is still about 15 percent nitrogen by weight, but you’re right that given the average application rates, folks won’t be applying as much nitrogen per square foot, which is great. I’m eager to hear how the product works for weed control. Keep us posted, Tom.

  • http://www.firebellylawncare.com Tom Kelly

    Paul,
    Our Liquid Gluten formulation is 1.5% Nitrogen and not 15%. This is a completely new formulation and the lack of nitrogen is what will make it a better product. The large amount of N that was involved with the granular gluten created a major contradiction. Prevent the weeds as they emerge…..feed the weeds if they’ve already emerged! With this new formulation that contradiction is no longer an issue.
    Tom

  • joe koniushesky

    i am into my third year of using corn gluten by blue seal in central connecticut. so far so good. last year just a few dandelions which were taken out by hand and some traces of crabgrass spot treated. i keep my grass cutting at medium height all season long, use my sprinkler system when i need it and use blue seal lawn food twice a season. my lawn is about 7,8 thousand square feet with a nice combination of sun and shade. thinking of going liquid next year.trying to stay as organic as possible because i have three ponds of considerable size on my property with some great fish in them.

  • http://www.sbmgarden.com Susan Macchia

    I think you’re correct when stating that the companies are overselling the weed prevention capabilities of corn gluten. However, if used correctly, it is nearly as effective in my experience. I use it on my lawn as a crabgrass preventer, making sure that I put it down after 3 consecutive days of >50 degree weather in the spring. This almost always coincides with the forsythia bloom. It works quite well for me and I don’t usually see crab grass until late August (when the second flush seems to appear). I also use corn gluten in my gardens as a weed preventer by applying it on top of the mulch. While it doesn’t work as well as preen, it works well enough. When I disturb the soil by planting or moving specimens, I simply re-apply it. My daily/weekly weeding is kept to a minimum as a result.

    I think that it’s not that corn gluten doesn’t work, it’s that it has to be used in a specific way. The companies marketing it aren’t clear about how to use it and in an effort to compete with traditional chenmical 4 step programs, customers perceive that it works the same.

    Susan

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  • http://thelawncareblog.com thelawnblog

    The corn gluten debate is far from over but this article gives much weight to the thinking amongst many lawn care amateurs and professionals alike that some products are more hype than help. Corn gluten is truly a nice fertilizer if you can get your hands on it “on the cheap.” As a weed preventative though; there are probably more and better alternatives.

  • Lon Moer

    thelawnblog said:

    “Corn gluten is truly a nice fertilizer if you can get your hands on it “on the cheap.” As a weed preventative though; there are probably more and better alternatives.”

    Please elaborate on what alternatives you are referring to. I am about to use CGM for the 1st time and already hand pull but, with arthritis progressing, I desperately need cheap, effective, environmentally safe alternatives.

  • Alyssa Owens

    Is the corn meal gluten organic? If not, does it contain the toxic hericide glyphosate?

    • Alyssa Owens

      oops, corn gluten, that is…

  • Paul Tukey

    Alyssa,
    Corn gluten meal is allowed in organic lawn care programs. It is a biproduct of the corn milling process and does not contact glyphosate or any synthetic additives.
    PT

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  • Shannon

    Is it okay to buy CGM from a feed mill (which is a fraction of the cost of the similar product marketed for gardening?) Will it be effective? I noticed that garden CGM seems to be 100% CGM while the CGM available for animal feed is only 60% CGM. Please share any thoughts/recommendations regarding the 60% CGM. (I’m trying not to price myself out!) Thanks so much!!

  • Paul Kim

    So what options are there? Corn gluten is just way beyond what I can afford. Looking at your how-to videos it seems important to do, but then reading this it’s less certain. Seems going organic doesn’t allow much for weed control specifically.

  • Heidi Sebastion

    Paul, sorry to say. but…If this is NOT organic corn its GMO corn, which if you are in the U.S.A, is 80 to 90%
    of U.S. corn…GMO corn is injected with pesticides…and is NOT
    organic. I used corn gluten ONCE on my lawn…and then realized it might
    be GMO, so I called the company and they confirmed that they did not
    use organic corn, so your spreading pesticides along with your GMO corn
    gluten. I have looked EVEYRWHERE to find corn gluten for weed control
    that is organic, and it is nowhere. I wish somebody sold it, because I would totally buy it. GREAT idea, if it really was
    organic, but since its not, your just spreading GMO crap all over your
    lawn. It really is too bad.

  • Dave

    This stuff is crap, plus if you are in the Chesapeake Bay watershed, over the course of a season you will end up putting down more nitrogen than is recommended.

  • Dsgustedjhgy

    I used Corn Gluten Meal late in the fall for in my hope that it would prevent winter weeds in the spring. (even though winter weeds are not that serious as they die out once the temperatures rise, in late spring, early summer)

    Not only did it work to prevent these weeds, my lawn is the greenest on the block right now, actually too green IMO for this time of year. Shouldn’t need to apply fertilizer until around Memorial day.

    I do plan on using a chemical crabgrass pre-emergent. I find I can apply at less than the recommended rate on the bag and still have good results.

  • ml01106

    Corn gluten is GMO!……….you know that. How can you not ban it totally?

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