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.
April 1st, 2010 at 9:59 am
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.
April 1st, 2010 at 11:15 am
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
April 1st, 2010 at 11:19 am
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.
April 1st, 2010 at 7:25 pm
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
April 5th, 2010 at 6:27 am
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.
April 5th, 2010 at 9:49 am
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
March 11th, 2011 at 9:44 pm
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.
March 15th, 2011 at 3:55 pm
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.
March 21st, 2011 at 12:37 pm
Is the corn meal gluten organic? If not, does it contain the toxic hericide glyphosate?
March 21st, 2011 at 12:43 pm
oops, corn gluten, that is…
March 21st, 2011 at 12:40 pm
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