Take Your Choice
With Organic Weed Killer * Alternative weed killers? Is it too much to compromise?
* Learn how weed killers work & how to use them,
* Chemical herbicides with disastrous effect.

Is there such a thing as an organic weed killer? Because let's face it, mix and spray chemical herbicide is a simple "no brainer" solution isn't it? Well, perhaps you should take a look below - because you may be surprised.

  • Unfortunately, some chemical herbicides can be persistent and then adversely affect the growth of what you plant next.
  • Moreover, these will contaminate your compost heap and prevent you recycling green waste.... ... you'll learn why this happens below.
  • The talk is about protecting children, pets etc... but it is the gardener who mixes and sprays chemical herbicides who is most at risk - and it's an unpleasant gardening job.
  • Pond life - frogs, fish etc... (and people) are susceptible to the ill-effects.
  • Plants become vulnerable to nutrient deficiency and disease.
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Below I compare the nasty synthesised herbicides with fast acting chemical alternatives for organic gardeners. But first let me highlight a few major problems with non organic herbicides - find friendly alternative weed killers here.

Some - Organic Weed Killers - Are More Friendly

You'll find more details about the friendly and the nasty synthesised herbicides below.

Sometimes however, there are intractable weeds (e.g. among paths, drives, walls and rock gardens) when expedience or a physical disability favour alternative solutions. The chemicals for this are best as a one-off use only. Repeat treatment may be needed on perennials, so you see it's really better to get stuck in properly if you can.

But if you want quick-use fast acting organic weed killers in your garden then the products on the links below are better organically and healthwise.

Here I compare Natural Organic Weed Killers with Nasty Artificial Herbicides. And what surprised me was that organic weed killers are reported to work better.

Natural Organic Weed Killers

These are simple substances with direct and obvious action. They destroy plant life for a short period. They are substances encountered naturally but in small quantities. So their presence is well-known and normally not harmful. But when applied in big doses the results are devastatingly obvious in a very short time. Examples include organic acids, heat from steam, boiling water and weed flamers and salt used in very small quantities on tiny patches. But see below first...

As always these methods need due caution. Yet they act at the point they are used and don't enter the food chain or organic waste stream. After treatment their damaging effect quickly dissipates. But note that 'natural' does not always mean 'safe' as these materials have been unnaturally concentrated.


Citric Acid, oils and ammonium soaps have become a 'cottage garden' alternative for those who dislike modern herbicides. But household Vinegar at 5% acetic acid is not strong enough; 15-20% acetic acid solutions are more effective. Although many organic gardeners wouldn't dream of even using these organic weed killers.

Nevertheless, these acids have been specially formulated in two ways as organic weed killers:
Burnout - where the active ingredients are actually  citric acid and clove oil and
Concern Weed Prevention Plus find how it works below - its all organic.

NOTE:- Household vinegar is unlikely to be cost effective against a branded organic weed killer that contains other materials that work synergistically. And citric acid is about 42 times stronger than acetic acid*1. Note that industrial vinegars should not be used in your organic garden. But find out more below... ...

These simple carbon based organic acids come without any surprise effects. The damage to plants is brutal and appears rapidly and even quicker on hot days. But Roundup can take 2 weeks to work.
Click to find one example from research   
Click to Close Box
In May 2002 PennState College of Agricultural Sciences found acetic acid gave over 90% control within 24 hours of application. With 3 treatments of 20% acetic acid, control remained above 90% even after 9 weeks (I assume this meant little re-growth & not reduced germination.)

But take care. They are 'blunt instruments' and you are best protecting yourself when using them. You must keep them off your cultivated plants, so apply on a calm evening.

The organic weed killer alternatives have a big plus over non-organic herbicide. They won't last to spoil your compost heap when you recycle dead plants, and they won't be hanging around when after 2 days you sow and re-plant.

Organic Weed Killer Alternatives

Click to Find Organic Weed Killers in Your Country.

How Do The Organic Weed Killers Work?

These organic weed killers are actually quite reactive. So they disrupt organic plant material simply by reacting with it and probably by making the cells leaky. They provide a short sharp shock before they're gone.

The ammonium fatty acid soap in Weed Aside will assist penetration and the ammonium molecule will lower the ph. But any left over ammonium will stick to clay as fertilizer if it doesn't gasify. Fatty acid ammonium is unlikely to move through soil. But as always care is needed to avoid direct spills into water.

In Burnout the clove oil may help the citric acid to be absorbed into the leaf as well as adding some phytotoxicity. Some suggestions that clove oil (commonly used in dentistry, food, cosmetics... ) is carcinogenic refer to large doses. And of course you shouldn't drink or breath any organic weed killer.

Probably the best use for these organic weed killers is in spot treatment and on paths, gravel, walls and difficult to dig places. But you should expect to treat perennials several times. Dandelions for example usually re-grow from roots. And don't forget that spraying them on lawns kills your grass. See more
on lawn weeds here.

The Natural Organic Weed Killer

Here I should also mention Concern from Safer Brand - an effective feed and weeder made of a natural substance (gluten) that is produced by some plant roots to suppress their competitors. Click here for more details or go straight to a natural feed & weed on this link.

Salt draws water out of cells to leave them dry, and salty soils kill plant roots. So target its application and use sparingly.

Excess salt poisons the soil. Many important organisms: bacteria, fungi, earthworms; will be killed by salinity and it shouldn't be used near your cultivated plants. For some gardeners it is an option for localised spot treatment against walls, and on drives and gravel where wash out can be contained. Remember, salt will not biodegrade, so regular use will be detrimental to surrounding areas.

Synthesised and Artificial Weed Killers
( Herbicides to be avoided )

These are more complex 'man-made' materials with indirect and subtle activity. They have no natural occurrence. They act on biochemical processes of growing plants from inside. This may be of concern to us because so much biochemistry is common to all living organisms. As they are not natural, living organisms are not adapted to their presence and we do not know the full effects of releasing them into the environment.

Some of these complex herbicides take time to act and their ill-effects in nature may not be immediately obvious. Should we turn the whole earth into a laboratory? Scientists like to do specific experiments on one process at a time, but this approach can miss complex interactions. And inactive components of a herbicide formulation (e.g. surfactants) can pose more problems than the weed killer itself. But by some legalistic trick these so-called inactive ingredients don't even need to be certified for use.

Here are some details on the nasty herbicides made from the molecules of organic chemistry but for good reason banned in organic gardening.

Potential Disaster With Chemical Herbicides

Clopryalid and Aminopyralid: the hormonal active ingredients in many herbicides. Aminopyralid is rapidly excreted in animal urine. Unfortunately manure has been contaminated with these herbicides, which in turn has ruined cultivated plants.*2

The chemical was withdrawn in U.K. but later reinstated. Nevertheless in 2010 the same problems had reappeared. Aminopyralid attaches to lignin (of plant cell walls). Hot composting is necessary to degrade it. Otherwise it persists and may affect plant growth in subsequent years. Compost made from lawn cuttings exposed to the weedkiller is therefore poisoned.*2

Glyphosate: is the active ingredient in Roundup. A report in 2009*3 detailed how the chemical can immobilise essential plant nutrients including manganese and potassium... ... ... The authors point to an increase in plant disease that results.

Glyphosate*4 works by blocking an enzyme that makes an essential protein. Genetically modified crops are unaffected by Roundup because they've been given a different enzyme to make that protein. Yet spraying Roundup leaves these plants nutrient deficient and disease susceptible.

And those nutrient deficiencies are feeding through to the human diet.

Roundup is supposed to be immobilised in soil. But excessive use in dry soils has led to large amounts being washed into rivers and streams after rain. It is not readily degraded in water and can have adverse affect on tadpoles to say the least.

Atrazine: (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine), This low cost weed killer has been associated*5 with contaminated drinking water causing birth defects, menstrual problems, and cancer in concentrations below EPA standards. Effects on insulin resistance and obesity and low sperm counts have also been associated with Atrazine. It is banned in Europe.

Atrazine*6 targets Photosystem II - an essential part of plant photosynthesis. But similar membrane structures may occur in animal mitochondria.

2,4,D or 2,4,Dichlorophenoxyacetic acid: a selective weed killer with hormonal activity on plants. It causes deformed plant growth. Manufacture produces several contaminants and dioxin type compounds may remain in the weedkiller. The Environment Agency notes that many organs and the unborn child are affected*7. But regulations aim to ensure that environmental exposure is too low for this to happen. Occupational exposure to 2,4,D is something else for you to consider. It is banned in some countries.

Regulating Weed Killers

Note that all these chemicals have licences for sale in particular countries (that may be reviewed). Regulatory bodies certify chemicals for specific uses sometimes under certain conditions. But there actual use is more difficult to control. Hence we increasingly see weeds that are now resistant to weed killers.

These synthetic chemical herbicides have been designed for use in agriculture. There transfer to gardening is inappropriate and really unnecessary. All concentrated forms that you have to mix before applying need extra care.

For any chemical mentioned here consider how you would feel if you discovered they had been used on food you bought as organic. Of course you must decide what is right for your garden.


  • RTU: Ready To Use - perhaps less risky for the gardener to apply, but no thank you.
  • EPA (The U.S. Environmental Protection Agency): E.P.A registration is a legal requirement for any pesticide/weed killer to be distributed in the U.S.A.
  • USDA (United States Department of Agriculture): Among other tasks they administer the NOP.
  • NOP (National Organic Program): Develops, implements, and administers national production, handling, and labelling standards for organic food production.
  • OMRI (Organic Materials Review Institute): provides an independent review of products intended for use in certified organic production under the National Organic Program. Note that products are only licensed for a specified use.
  • The Soil Association certifies organic growers in the U.K.

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By Michael E. J. Scott.
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