A veritable hornet’s nest of controversy surrounds the meaning of the term “organic weed killers.” The average gardener or DIY lawn care guy/gal is not interested in the dust-up and turf wars about organic weed killers raging among government agencies today. But just so you know, there are debates between the Dept. of Agriculture and the EPA, the National Organic Program and the Organic Materials Review Institute. In addition, there are the many other self-described organic standards bodies. No, the average gardener just wants to know what he/she can use to get rid of weeds that is “natural” and “won’t hurt the environment.” And by “natural weed killers,” he/she doesn’t want some wry, winking answer that suggests you just pull them up by the roots or hoe them out …. Or “mulch them out of existence.” So is there such a thing as natural or organic weed control, and how good do they work?

In sympathy with the average homeowner, what follows here are what are called by the experts “minimum risk” ingredients that will kill weeds. The “minimum risk” as used here refers to risk resulting in environmental damage or impact. Also the “bad” weed killers (e.g., Round-Up, et al) are termed “synthetic” weed killers.

All weed killers, regardless of risk, are herein termed “herbicides.”

Because so much of the information on the natural minimum risk weed killers is ad hoc and yet to be scientifically verified, what follows is unfortunately hearsay and anecdotal. That is, certain gardeners swear to their efficacy, but the ratios and mixtures of ingredients vary from gardener to gardener. One might add, as a further cautionary note, that if you pour enough of anything on a weed it’s likely to die, whether it’s soapsuds, beer or garlic juice. Anything would, for that matter.

The University of Florida Department of Agriculture has posted the following table on its website as “Minimum Risk Herbicides.” They do not go so far as to recommend solutions, ratios or mixtures or specify which ingredient works best on which kind of weed. However, gardening sites and blogs are rife with such recommendations and we would “recommend” you check them out.
Castor Oil (U.S.P. or equivalent) – Linseed Oil – Cedar Oil – Malic Acid* – Cinnamon* and Cinnamon Oil* – Mint* and Mint Oil* – Citric Acid* – Peppermint* and Peppermint Oil* – Citronella and Citronella Oil -Phenethyl Propionate (2-phenylethyl propionate) – Cloves* and Clove Oil* – Potassium Sorbate – Corn Gluten Meal* – Putrescent Whole Egg Solids  – Corn Oil* – Rosemary* and Rosemary Oil* – Cottonseed Oil* – Sesame* (includes ground Sesame plant stalks) and Sesame Oil* – Dried Blood – Sodium Chloride (common salt)* – Eugenol – Sodium Lauryl Sulfate – Garlic* and Garlic Oil* – Soybean Oil – Geraniol 29. Thyme* and Thyme Oil* – Geranium Oil – White Pepper* – Lauryl Sulfate – Zinc Metal Strips (consisting solely of zinc metal and impurities) – Lemon Grass Oil* * These active ingredients are exempt for use on all food commodities from the requirement of a tolerance on all raw agricultural commodities at 40 CFR 180.1164(d).

“Putrescent eggs” gets my vote as the grossest and possibly the most effective minimum risk herbicide on the chart. They very well may make the gardener handling them sick too, not just the weed.

At any rate, since all of these ingredients are readily available, fairly cheap and not normally harmful to people, the intrepid gardener might employ the tried and true empirical method and try these out as potions mixed with varying amounts of H2 O, and just see what exactly it does to the crab grass. Once he/she hits the bullseye, he/she might send a note along to the Profs at the University of Florida Dept. of Agriculture with the right mix. They’d probably appreciate the tip.

Not to be outdone by ordinary gardeners, the big chemical companies are jumping on the green wagon and have brought out a few “natural” herbicides that are now on store shelves. Look for more to follow unless Ed Brown down the street doesn’t beat them to it with his all-purpose herbicide peppermint oil spray.

Of course, the best thing to do with weeds naturally is to prevent them, and corn gluten meal makes a great weed preventer. Also, if you want to try out some natural organic weed killers, below are some for you to test out.

If you guys have spent any time around here, you know that I am a big fan of Milorganite for lawns. It is a great slow release fertilizer that also contains iron, and iron makes bluegrass lawns deep blue! But enough of that, read on and learn. A friend of mine wrote this quick review on Milorganite:

Milorganite Organic Lawn Fertilizer is natural slow-release organic nitrogen fertilizer. Proponents of organic slow release nitrogen fertilizers praise Milorganite for its slow delivery of naturally occurring microbial nutrients deep into the roots of the grass, a process they believe is preferable to the instant massive release of chemicals characteristic of synthetic chemical fertilizers. Synthetic chemical fertilizers carry with them the potential for burning the grass because of the large amounts of nitrogen and salts immediately unleashed upon application. Milorganite Organic lawn Fertilizer releases nutrients and minerals slowly and only as the grass is able to use and absorb them. Their release is actually triggered by the microbials in the grass itself when the grass needs to feed upon the organic fertilizer.

Milorganite is made from activated biosolids (sewage sludge) and contains 6% nitrogen, 2% phosporous and 0% potassium, lower ratios of each than the ratios contained in synthetically blended fertilizers, but more effective in feeding lawns, advocates say. The slow release characteristics of Milorganite guarantees groundwater is not polluted by fertilizer runoff into creeks, lakes and rivers.

The absence of salt content in Milorganite Organic Fertilizer prevents the drying and burning of lawns, particularly in the hot summer months, something which can occur with quick releasing fertilizers you find on the shelves of local big box stores.

The presence of 4% iron in Milorganite also creates a deeper green in lawns than synthetic chemical fertilizers and helps build a deeper underlying root system or turf, rather than simply increase the height of the grass itself from a thin root base, a common effect of synthetic chemical fertilizers. This results in a healthier lawn overall and one that does not require extra mowing as a result of rapidly growing grass leaves, or rampant “top growth,” a typical result of applications of synthetic chemical fertilizers.

Milorganite Organic Fertilizer is child and pet safe and releases no dust into the atmosphere, which could be inhaled by people and pets, and which diminishes the actual amount of fertilizer that actually is available to treat the lawn.

A 50-pound bag of Milorganite will treat 3100 square feet of lawn and does not require watering in. Watering in will make the fertilizer more quickly available to the grass and the grass will show faster results from the fertilizer application, but it is not required. Because it is essentially “dust free,” Milorganite Organic Fertilizer will not blow off the grass in windy weather prior to rainfall or watering, which drives the fertilizer into the roots and allows the roots to “feed” on the available nutrients.

Milorganite Organic Fertilizer is widely available at nurseries and garden centers and is one of the most popular natural organic fertilizers on the market. If you are looking to “go green” with your lawn care regimen, give Milorganite a shot.

Wanna know when is the best time to put down Milorganite? How about an entire year’s fertilizer treatment schedule? Get my e-book and learn it! Organic Lawn Fertilizer Schedule

Corn Gluten Meal Organic Fertilizer

Corn gluten is used for many lawn and garden applications, but the two most popular are as an organic natural fertilizer and as an organic crab grass control or preventative. If you are thinking of using it on your lawn, read this before you start.

What Is Corn Gluten Meal?

Corn gluten meal is a by-product or leftover from when companies make corn starch and corn syrup. When you get it at the store or local garden and lawn center, you will find it in 40 or 50lb bags in pellet or granular form. Overall, it contains around 10% nitrogen. Nitrogen is pretty much the essential nutrient that turns grass green, and corn gluten meal has a very solid and stable amount naturally, making it a GREAT choice for an organic fertilizer.

Is Corn Gluten Meal A Good Organic Fertilizer?

Yes, it is! Corn gluten contains a very nice amount of nitrogen, and because it is organic, it is naturally slow releasing. This means that it feeds the lawn slowly over time, making a nice impact on plant growth without pushing the turf unhealthily. So many of today’s synthetic fertilizers are full of quick release super hydrated nitrogen that pushes the growth of grass plants, almost like giving them a sugar rush that will end in a crash at some point. Organic fertilizers like corn gluten won’t do this.

How Does Corn Gluten Prevent Crab Grass?

Corn gluten meal, when applied early enough in the season, will build up in the soil line and prevent annual crab grass with some fairly good results. The key is you have to get it down just after the snow goes away. If you wait too long, you will not get very good control. I also recommend you NOT apply corn gluten in heavily shaded areas because:

1) crab grass does not usually grow in shady areas

2) the corn gluten will build up in the soil and actually thin out the grass in shaded areas. This grass is weak already from lack of sunlight.