(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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