Is There An Organic Choice
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SAFER ORGANIC WEED CONTROL
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Here I look at a number of weed killers under 2 headings – Natural Weed Killers and Nasty Artificial Weed Killers.
Let's look at what does work in organic gardening.
Natural Weed Killers
These are simple substances with a direct and obvious action. They destroy plant life for a short period. They are substances encountered naturally but in small quantities. Their presence is well-known and normally not harmful. But when applied in big doses the results are usually devastatingly obvious in a very short time. Examples include salt, weak organic acids, alcohol, heat from steam, boiling water, and weed flamers.As always these methods need due caution. But they act at the point they are used and don't enter the food chain. After treatment their damaging effect quickly dissipates. Even the treated plants may sometimes recover.
See details of Natural Weed Killers below
ACETIC ACID WEED KILLERS
Now specially formulated as an organic herbicide called Burnout. It is made of Acetic Acid (Vinegar) along with other weak organic acids and oils. It has become a 'cottage garden' alternative for those who dislike modern herbicides. Acid is a very blunt instrument, changing the chemistry around roots and in cell sap, to affect the plant in many ways. The damage to plants appears rapidly and even quicker on hot days. After all the aim is to kill them.Household Vinegar at 5% acetic acid is not strong enough; 15-20% acetic acid solutions are more effective. Avoid industrial vinegars in the organic garden.
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.
The soil can be acidified but this type of weak organic acid lasts only a few days. That's not long enough to have any lasting affect on earthworms, soil, or organic matter breakdown. The good news is that it won’t cause any insidious harm to pets or children. Take care not splash your eyes.
Garden products based on acetic acid are now available for organic gardeners as alternative herbicides.
Burnout
is available in America from Gardeners Supply and contains lemon and oils such as clove oil as well as acetic acid. It can kill Canadian Thistle, Clover, Dandelion, Foxtail, Ivy Leaf, Milkweed, Pigweed, Poison Hemlock, Ragweed, Quack grass, Bluegrass, plus mosses, liverworts and more. It is not selective and harms the plants it touches.
FATTY ACID WEED KILLERS
These work by dissolving the plant membranes, making them leaky. The plants dehydrate. Of the 2 products I estimate that fatty acids have the edge. I’m guessing that they are less broadly harmful, that their soapy properties aid uptake and reduce spreading in the soil. You can try a branded formulation with Weed-Aside available in America from GardensAlive. This one works well on spot treating bindweed.Obviously you must avoid spraying these on cultivated plants. So it’s probably best confined to spot treatments, perhaps when you need extra help with weed control and to avoid the seriously nasty herbicides.
Remember, if you burn a hole in the lawn with these treatments it is important to fill the empty space as soon as possible. Sow seed and promote strong thick re-growth with the help of organic fertilizers. If your lawn becomes patchy it will become weedier. Always prevent weed seeds being distributed.
Note: The reason Burnout and similar products are not available in Europe is due to European legislation and renaming of acetic acid or vinegar as a weed killer. It costs about £2.5 million to test these products against stringent E.U. standards.ORGANIC GERMINATION INHIBITOR
I should also mention WOWr - an effective feed and weed solution made of a natural substance. Click here for my details on WOWr or go straight to feed & weed product offers on this link .
SALT WEED KILLERS
Geoff Hamilton recommended a spoon full of salt to kill Dandelions and the like. 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. It will eventually wash out, even so I would not use it on land intended for cultivating plants. For some gardeners it is an option to consider with drives and gravel areas where plants are not intended to grow and where run off can be contained. Remember, salt will not biodegrade, so regular use will eventually be detrimental to surrounding areas.
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 effect the biochemical processes of growing plants from within. Examples of these are 2 4 D, Atrazine, Glyphosate, Clopyralid. They may be described as organic by chemists, but are banned in organic gardening.As they are not produced naturally, organisms are not adapted to their presence and we do not know the full effects of releasing them into the environment. They can work in tiny quantities.
Many of these complex herbicides take time to act and likewise in nature their ill effects may not be immediately obvious. The chemical interactions are complex. It is impossible to design a thorough investigation cheaply, if at all. Scientists like to do specific experiments on one process at a time, but this approach only scrapes the surface. Sometimes the inactive components of a herbicide formulation (e.g. surfactants) pose more problems than the weed killer itself.
Are we to study the effect on thousands of chemical processes and their interactions? Should we turn the whole earth into a laboratory? No, but especially no when there is a better solution.
So let's take a look at the performance of Natural Weed Killers on this link.
Further information on weed killers
I will be posting more information on the ARTIFICIAL HERBICIDES soon... please come back.BOOKS ABOUT WEEDS AND WEED KILLERS
For more information on making / using shrub fertilizer try these books.
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Weeds: Friend or Foe? - An Illustrated Guide to Identifying Taming and Using Weeds By Sally Roth & Anna Dourado 
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