Killing weeds in a more earth friendly way

(First published December 2008, updated April 2010)

Instead of using really nasty commercial chemicals to rid your garden of noxious weeds, where possible just try using water.

Yes, water :)

The trick is to boil it first of course. Boiling water is particularly effective for use on weeds in the expansion joints on driveways and paths. 

Other greener options for killing weeds (depending on the type) that I’ve had some success with:

– Neat white vinegar is good as an earth friendly broad leaf weed killer. Vinegar is most effective when applied on a sunny day. Use in a targeted way.

– A strong saline (salt) solution can be used on gravel driveways and where weeds have sprung up between cracks or joins in pavers. It’s probably best not to use this in open areas where other plants are close by as repeated applications can cause the salt to leach over a wider area, kill other plants and prevent new plants from growing in the affected area. It’s for this reason that salt is also a good way to prevent weeds from growing again between pavers.

Lemon juice is also said to be highly effective in killing weeds of all types and it will break down very quickly.

There are also quite a few “green” commercial products around (none of which I’ve tried), but if you do need to buy mainstream commercial chemical preparations as an action of last resort, I recommend glyphosate – it’s probably the lesser of the evils in terms of commercial herbicides; so let’s now look at harm minimization using this product.

Sold under hundreds of different brand names, glyphosate supposedly breaks down very quickly, although the video “The World According To Monsanto” challenges that claim. Information from the Center for Ethics and Toxics (CETOS) says glyphosate binds to many soil types and clay materials, making it immobile in many soils and can move into groundwater when the soil is washed into waterways. CETOS says its binding to soil particles is also responsible for inhibiting soil micro-organisms long after chronic exposure.

That said, glyphosate is a very economical and effective broad spectrum herbicide. A $4 bottle of generic branded glyphosate is just as effective as a $10 bottle of popular brand name weed killer containing glyphosate if the concentrations are the same.

When choosing a glyphosate based product, be aware of the percentage of glyphosate in different products as it can vary widely. The concentration will be mentioned on the label. For example; a $4 bottle of weed killer may have 10% glyphosate and a $6 bottle may have 20% – so the latter, although more expensive, is the better deal. Equally as important, by taking note of the percentage whenever you change brands, it acts as a flag to check the application instructions – as you may need to use less or more of it.

It can take up to 7 days after application before the weed starts to turn brown, particularly if it’s a large one – so don’t be tempted to apply more if it doesn’t keel over within a couple of days. When the weed does finally start to show signs of stress, the end comes pretty quickly. Glyphosate should be applied when there’s no chance of rain within 6 hours of application.

To further reduce environmental risks, it’s so important to only use the amount as directed on the bottle – using more won’t kill the weeds any faster or more effectively. Also invest in a hand pump sprayer – the money you outlay on the sprayer will be offset by the reduction of glyphosate you’ll need to use if, for example, you would otherwise use a watering can to apply it. Less chemical – less collateral damage on the environment and less damage to your wallet also.
By using it sparingly and according to directions, you’ll also reduce the risks of weeds building up resistance – and glyphosate resistance has already been reported. This is an important and disturbing development as glyphosate is to mainstream agriculture what penicillin was to to modern medicine. If resistance becomes common, I shudder to think about the environmental effects of any chemical that replaces it.
As always though, prevention is better than cure. One of the best ways to prevent weeds from growing is to use mulch, which has the added benefit of providing nutrients to plants and saving water in your garden. Of course, there’s always the old fashioned way of getting rid of weeds too – by hand – it’s great exercise if you’re physically able to do it and can help put you more in touch with what’s happening in your garden. It’s amazing what you’ll discover about your garden if you’re a little closer to soil level.

Also bear in mind that some “weeds” are actually useful plants.
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