Organic Weed Control: How Effective Is It?

>> Friday, February 11, 2011

Many gardeners prefer to get rid of weeds without using manmade chemicals.

Anything that makes getting rid of weeds is a good thing, but using something that is natural, easier and safer to use is better. And if it does not leave a poisonous residue that hangs around for years, well, that’s just a bonus.

W. Thomas Lanini, weed ecologist for the California Cooperative Extension Service, recently investigated the effectiveness of a group of organic herbicides that are all contact herbicides with no residual activity. The active ingredient in these products was either acetic acid (vinegar) or various plant oils that work by stripping away the waxy cuticle on the leaves, causing them to wilt and dry up. They included WeedPharm (20% acetic acid); GreenMatch (55% d-limonene, which is the major component of the oil extracted from citrus rinds); GreenMatch Ex (50% lemongrass oil); Maratec (50% clove oil); and WeedZap (45% clove oil and 45% cinnamon oil).

Lanini found that these products gave reasonably effective control of broadleaf weeds such as pigweed if weeds were treated when they were still young. Treatments to plants that were 12 days old gave a much higher chance of effective control than to weeds emerging later.

He also found that good spray coverage was essential and that adding organic surfactants or spreaders to the herbicides improved control. Most of the organic herbicides also worked best at temperatures above 75 degrees.


Greg February 11, 2011 at 2:00 PM  

I just read your post and have to ask: How effective is organic weed control?
You pose the question, but there seems to be no real answer. Comparisons? Actual results?
The post just left me wondering how effective organic weed control really is.

Greg W February 12, 2011 at 5:04 AM  

Hello Greg
I have used several of these plant oils - mentioned in the post – in homemade recipes but always return to vinegar. Vinegar is simply more effective than the oils. When using vinegar against weeds coming up through the seams in my driveway it is very effective, but must be reapplied each time new weeds appear because vinegar does not linger, which is one of the positive aspects about using organic weed control. When using vinegar in the garden you must be careful not to allow it to splash onto desirable plants because it is an indiscriminate herbicide.

You can dilute vinegar by up to 50 percent or more with good results but I prefer to use it full strength.

In my earlier days of gardening I was guilty of using chemical herbicides (glyphosate found in Roundup and 2,4-D found in Weed B Gon) but became concerned of their residual effects and began researching the use of more organic methods. They seemed to work more effectively than organics but the fact that they are man-made chemicals turned me against them.

Organic herbicides need to be applied more often (every couple of days) and you really need to apply it to weeds while they are young (less than two weeks old). Once the weeds become more mature the effectiveness of organic herbicides falls off greatly. At that point you must resort to a hoe or pull them up by hand.

I hope this clears up any questions. I apologize for not being able to supply exact scientific data but I can only go on what I experience.

Greg February 14, 2011 at 11:43 AM  

Thanks, for the extra help. Can it be sprayed, or should it be applied to the leaves by hand? I've always been under the idea that if I'm getting down and 'painting' it on the leaves I might as well just pull them. What are your thoughts?

Greg W February 15, 2011 at 6:00 AM  

I follow that same school of thought. In fact if I’m out there on my knees anyway I just slice the roots with a hand trowel and pull them up. For the really stubborn weeds, such as bindweed aka field morning glory, the ‘paint’ treatment works best in Spring when they are actively growing and again in Autumn when they are storing energy for over winter.

I have a one gallon sprayer that allows me to pump up the pressure, with the spray-wand set to ‘stream’ I can get pretty good accuracy. For smaller jobs a spray bottle will do, but most don’t have very good spray heads for pin-point streaming. If you can find a good, dependable spray head hang on to it.

Gardener February 16, 2011 at 1:32 PM  

Thanks for the help. I've been trying to get rid of all the chemicals in my yard, and reading up for the coming spring.

Greg W February 17, 2011 at 6:30 AM  

You are welcome Gardener,
Just keep in mind the organic method may require repeated spraying, if you don't get the weeds early enough. But the goal to get rid of the chemicals is well worth it, in my opinion.

Good luck

pest control utah October 31, 2011 at 4:37 PM  

Organic pest control methods are 100 % natural and pose no threat to your health or the environment.

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