Organic Broad-Spectrum Herbicide Recipe (Wild-Foraged from ‘Weeds’)

Organic Broad-Spectrum Herbicide Recipe (Wild-Foraged from ‘Weeds’)

Chemical warfare isn’t something generally associated with plants – they are more associated with peace & serenity, harmony & working in community (the colour GREEN represents LOVE).  The truth is – just like people, not all of them are kind.  Taking a little time to observe what species are dominant & by how much can uncover a grisly tale – for plants, that is!  Allelopathic species are genocidal, literally!  Translating as “causing those with different genetics to suffer”, these green-ones are nasty!  By releasing growth inhibiting substances into the soil they kill all other species – up to 100%.  They are killer-plants…and develop natural monoculture worldwide.  Ever noticed how Australia is covered in almost nothing – but eucalyptus…or how camphor laurel can take over a river system in just a few years…or how amaranth is so easy to grow?  Yes, you’ve got it – it’s because everyone else is DEAD!  Killed by these murderous allelopaths.

So, what do we do with these guys?  With an ironic flip of the coin – do WE become the genocidal killers & pull THEM out?  Or just let ‘em grow & hope for the best?  Well that depends on your garden needs.  If you don’t need that space – why bother doing anything at all (just let nature take its course).  But if you need that space, why not harvest them as a crop.  Just think about it – they contain a substance which can kill plants.  They are a NATURAL BROAD-SPECTRUM HERBICIDE.  So how exactly do we do this?

We can release the target allelopathic substance held within the plant cells by freezing which will burst the cells open.  Ensure the whole plant has been shredded into small pieces, add water then freeze + thaw up to three times.  On the third defrost, blend & strain the solids out  (make sure all seeds are destroyed in the blender).  Voila – you have a solution of naturally derived & locally foraged broad-spectrum herbicide.  Just like any plant material, keep it fresh by storing in the fridge (for up to three weeks) & freezer for long term storage (no limits here, keep it for eternity if you like).  Be sure to label clearly as you DON’T want to get this stuff mixed up with your Kombucha!

So how much should we use?  A study done in Japanese rice fields found the optimum application rate to be around 100 grams per square metre when applied 1-5 days at the start of the growing season (2).  In other words – the seed won’t sprout & the plant won’t grow.  Let’s round this off to be ¼ – ½ of a soft drink bottle in liquid extract.  Transfer to a bottle & use as a foliar spray directly onto the flowers or seed of the unwanted plants or pour into a watering can & soak into your garden soil (where the unwanted seed would generally sprout if left untreated).  If you are planning on using over a large area – you may wish to trial on a smaller plot first.  Happy killing – I mean, gardening!

This is ORGANIC GARDENING at it’s best!


For more information download:

“Allelopathy an Environmentally Friendly Method for Weed Control”

Or follow a research project on this topic by Harper Adam’s University, Kurdistan Region Government and the Ministry of Higher Education here:

“Weed control using allelopathic plant species”


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About The Author

Chrissy-Tiina Laurikainen

In person + online permaculture teacher. Online permaculture consultant. Upkeep of a 30 acre rural property (using permaculture & other agroecological techniques). A communal research laboratory focusing on free innovation in the works. Doing what I can to support LIFE on planet Earth!!

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3 thoughts on “Organic Broad-Spectrum Herbicide Recipe (Wild-Foraged from ‘Weeds’)

  1. Hello

    I plan to replace unwanted grass with a better lawn and could buy turf. I do not want to use chemicals that could harm humans or the soil or anything else nearby.

    I thought of another way to kill grass that I can share with you that uses a hot plate or heater that could be automatically moved. A special electric blanket could also be made to heat the surface of the ground and soil. Do you know of anything like this or anyone that has done it? People use solarization that works. However, this takes months and is best done with clear UV proof plastic that is hard and expensive to get. It also requires very hot weather that we normally do not have.

    Also, I have some unwanted grass that has produced seed heads that developed a week or two ago. I am wondering if it is likely that they would have seed that could be mature that could be a problem if I mowed the grass? I do not want to spread it on to the good lawn. Could I mow it or would it be best to first either burn the seed heads with a flame torch or break the seed heads off and put them in a bag? If so, would it be better to burn them or break them off? I thought if I mowed without removing or burning the seed heads first, it may spread the seed around more. Is there a way to tell if the seed heads have seed that is mature enough to grow?

    Regards Richard.

    • Hi Richard,

      It sounds like your lawn is no longer satisfying your needs. I suggest to create a list of = why you wish to change it + other needs (food etc).

      Then focus on growing plants which meet all your needs. If you wish to continue with the grasslands habitat, include plants which fit into the following 3 layers:

      1. Groundcovers.
      2. Underground layer – root vegetables & other root crops.
      3. Herbaceous layer – flowers, herbal teas, medicinal herbs etc.

      With all 3 layers the habitat will be self-supportive & need no care…once established, harvest your food & enjoy the view!

      For fast growing (pioneer) species – herbaceous layer:

      With 3 layers it’s a polyculture system & mimics nature = no maintenance needed in nature, it looks after itself. The diverse plants supply each other with nutrients via micro-organisms in the soil. And water will be collected via the diurnal dew & fog = it will not need to be watered.

      Organic nutrients are produced from micro-organisms in the soil. They break down organic material into soluble nutrients that can be taken up by the plant roots. Cumulatively, they are known as ‘soil life’. Like all life, they are damaged (killed) by sunlight & heat. Sunlight or heat will further dry the soil & turn it to dust. It will be dead soil unable to support plants without nutrient inputs = this is work!

      If you wish to create work for yourself, focus on killing the soil. If you wish to spend your time on other more enjoyable tasks = create a natural habitat which will care for itself.


      1. Cover the existing lawn with cardboard & mulch. Give it a good regular watering & ensure it does not dry out.
      2. Allow a couple of weeks to pass. This will grow a healthy, living soil underneath (micro-organisms) as the old lawn dies & is decomposed into rich, organic compost.
      3. Punch holes into the cardboard & plant the new species (seed or seedlings). Place randomly & mix the species up.
      4. Keep watered until the new plants are established & the ground is completely covered with living plants.


      1. Allow your new grasslands habitat to care for itself.
      2. Water only during drought or if there is a break in the plant cover (i.e. you can see the ground).
      3. Harvest your tea, herbs, root crops as you need.
      4. Return unwanted material (i.e. leaves, skin from peeling root crops, trimmings etc) to return to the area so it can build new soil.

      More info on soil health…

      Don’t forget to post the photos of what happens when you trust nature to do the work for you! So we can learn from each other. Enjoy!

  2. P.S. You can’t get better than local, native species. They are perfectly suited to the climate & support the surrounding environment. In turn, your area will receive support back. (This may look like added nutrients via kangaroo droppings. Possums bringing in new seed, saving you time in having to plant support species. Insects pollinating your crops.)

    Give yourself a break – let nature do the work for you!

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