Introduction: Making Liquid Fertilizer From Weeds

Picture of Making Liquid Fertilizer From Weeds

Weeds, we've all got them!

Let's turn them into something useful.

Now I don't like putting weeds into my compost heap as you can end up with them spreading, the alternative is usually to burn them but they are full of nutrients so this is a bit of a waste.

Why not try to recover the nutrients and at the same time render the seeds from the weeds inert.

All you need for this is:-

A Container (in my case I have used a plastic 45 gallon barrel)

Weeds (no shortage of those!)


I have actually looked iat some past I'bles since publishing and refer you to tim_n nettle fertiliser from 2010 i hadn't realised however it does give me the opportunity to enter the REMIX contest :-)

Step 1: Gather Your Materials

Picture of Gather Your Materials

As I said I used a 45 gallon plastic barrel, found in a skip, originally container for mortar plasticiser.

I have a large garden so wanted a big container, if you want to make less then use a smaller one

I washed the barrel out just to make sure there were no nasties in it

The Weeds, try to find deep rooted stuff, thistles are excellent, but also dock, dandelions etc - dig the whole thing out including the tap root

You can also use other deep rooted "non weed" plants like Comfrey

Step 2: Fill the Barrel and Add Water

Picture of Fill the Barrel and Add Water

Top up the barrel with weeds and fill with water

Cover and leave for 2 weeks minimum

Step 3: Mmmmmmmmmm Stinky

Picture of Mmmmmmmmmm Stinky

After 2 weeks you end up with this slightly smelly tea (or soup), the smell isn't too bad - you wouldn't want it in your house but it is fine a few yards away!

Water this soup down 15 to 1 and then water on your plants about once a week

Top the barrel back up when you have finished for the day and it will be back to full strength in a few days

I change out the weeds about every 4-6 months, the old ones are almost completely decomposed and can now go into the compost.

This process releases all the good nutrients into the water so you get the following (amongst others)









I watered my Kumara with this and won the local veg competition with a 1.6kg specimen (See Photo!), it also did wonders for my citrus trees, which were spindly and lacking and now are big and bushy.


A few people have commented about decomposition of seed heads, I generally get my weeds before they have gone to seed, but if you think that the seed heads may still be viable then I advise you to burn the weeds after you remove them from the soup

Edit 2

I watered my paddocks with this mix at a ratio of 10 to 1 I used approx 7 lires (70 of mixed) for an acre, it promotes grass growth and because the soil is richer the weeds don't seem to like it (I believe they prefer poorer conditions) Once you have sprayed your grass keep livestock off of it for 10 days to allow the grass to grow and any nasties to dissipate. Ideally spray before a rainstorm if possible (or during like I did!! :-( )

I will endeavour to answer all questions, and appreciate the comments and advice received so far


LadyMoon (author)2017-05-18

I used a tall trash can with a tight fitting lid, installed a faucet 3 inches from the bottom, put a round paver in the botton, set a plastic milk crate on the paver and put in a mesh bag for the weeds. I can get the tea without opening the lid and I can add weeds as I get them

buck2217 (author)LadyMoon2017-05-20

Sounds like a good setup

davidj31 (author)2015-08-31

I made it but no image yet.

Cut top off a plastic 15 gallon drum. Threw in weeds I had pulled just 2 days before reading this instruct. Filled with enough water to cover weeds, placed brick on top to keep 'em submerged. Smell is something else, can't keep it in the garage so it sits outside. I'm hoping the seeds compost and will find out in a few months.

buck2217 (author)davidj312015-08-31

Cool, put some plastic or tin (or even cardboard) over the top and the smell will be contained

Berkana (author)2015-08-17

I have some suggestions based on my knowledge of the biology of compost and some of the processes involved.

The stinky odor comes from rot and anaerobic fermentation, and is not a good thing, and our recognition of the stench warns us of this. Methane is also released by this kind of fermentation, and the methane is a pollutant.

The benefits from the weed material can be gained without the stench by using other bacteria to break down the material in the form of pickling. If you damp down the weeds, put down a stone or something to weigh down the weeds, and start it with bokashi starter (I'm sure there are instructables on bokashi pre-compost fermentation), you will still break down the weeds and will still have a nutrient rich liquid byproduct, but it will not stink; it will smell like pickles. Essentially speaking, this kind of fermentation forms a sort of sauerkraut out of the weeds, pickling them. When buried in the ground, worms go nuts over pickled plant matter, and will eat it up preferentially, because it is easier for them to digest.

The side benefit of bokashi and lactic acid fermentation (somewhat of a misnomer; lactic acid is not the the only nor even the primary acid that is produced) is that the weak organic acids produced in the process boost the cation exchange capacity of the soil, making it more fertile independently of the nutrient content of the liquid.

Try it out. It's not that different from what you're currently doing, but it will definitely stink less.

Shindou (author)Berkana2015-08-20

Great idea, but I think you have changed the process enough to warrant making your own 'ible. I for one would LOVE to see how to do that entire process end to end.

buck2217 (author)Berkana2015-08-17

TBH it is only a mild smell sort of like earthy compost, if it was too "ripe" then I would question it

Spike63 (author)2015-08-18

Another point, who wants to waste beer on a garden project? It should be used for keeping the man happy and I don't know anything about that Cola rubbish...
I'm always in awe of people who can find odd things to do with beer, maybe someone can come up with a 'structable to make my day! Apart from making our own, natch!

buck2217 (author)Spike632015-08-18

Beer is for drinking not gardening, a bad beer is better than a good coke!

Spike63 (author)2015-08-18

I just pour a little olive oil on the surface, that kills the li'l beggars! Organic if you like...!

buck2217 (author)Spike632015-08-18

If you want to be cheap use any old cooking oil (rather than more expensive olive oil)

rlove4 (author)2015-08-17

I do this with Comfrey and Nettle every September and let sit till Spring. Lay out a net, pile up the leaves then roll up or gather the corners and tie with string. Put the bundle in the container of water with one end of the string hanging out the top with a bit wood on, so once a month you can (hold your breath, it stinks) lift the lid and pull the bundle up to the top to keep it all circulating. In Spring it can be lifted out and composted / burnt / binned and leaves the liquor free of solids.

buck2217 (author)rlove42015-08-17

I just fish the rotted weeds out with a rake!

ooohlaa (author)2015-08-16

Hi ... thanx for this. I make compost tea all the time but never thought to use weeds. I use compost from my pile. I carefully cart off weeds to the local recycle station but now I will do it your way. I do get LOTS of mosquitoes, they love compost moisture, even with a lid on. Do you have any skeeter problems? I added some kitchen soap to the water to kill the larvae but not crazy about doing that. Here in Fl all insects are legion!

namora (author)ooohlaa2015-08-16

Instructables has offered several effective mosquito traps that may prove useful for you.

ooohlaa (author)namora2015-08-17

Thanx, I did try a few with minimal results. I did th whole you tube tutorial on such things. I just have too much vegetation and trees on 1/2 acre, very lush, and farm lands all around with tall grass for them to breed in.

ндогонят (author)ooohlaa2015-08-16

Seeds are designed by Nature to remain dormant as long as possible until the "right" conditions occur, so a 4-6 months soaking is not gonna kill them unless you get some serious help from bacteria (the smell says you got that help)... and there are lots of bacteria you really don't want to see in your "soup" (e.g the omnipresent clostridium botulinum, guess why...), especially if you fill your jar to the top (much "better" for anaerobic composting).
On my side, I don't have such a big garden, so my needs are much lower. I soak 3 to 5 kg of earth in a plastic bag and put it full power into the microwave. That really kills everything and there is no risk of botulinic toxin contamination (that's the way the clostridium kills all other bacteria) -- if you intend to eat what you grow...

ooohlaa (author)ндогонят2015-08-17

Thanx for details. I am an avid follower of Praxxus on you tube, fabulous organic farmer and he said he gets great results with very little soil amendments, and just compost tea. He says it doesn't matter if its anaerobic, or stinky smelly, it still works. I have pretty much noticed the same but nowhere his results. Even on barren soil he works it. I make tea with my compost and "cook it" 48 hours, then only slightly dilute it and add more water a few times, then dump and start with fresh compost. Also all kinds of leaves work pretty well. But I also use other fertilizers but he does not and you should see his results. He's onto something with his simple methods. Dunno about clostridium, have to check it out bec I do eat what I grow and a microwave would not work.

Thanks. Good points.

I generally burn as many seed heads as I can and even the "old" weeds will probably be burnt before adding to compost, however after the soaking anything that goes into the compost heap is generally in there for at least 6 months

Weed seeds from most species will fully decompose in a fully anaerobic digester in a few weeks.

buck2217 (author)ooohlaa2015-08-16

If you keep a lid on the barrel then hopefully it will keep the mozzies down, we have some mozzies etc but also 20 free ranging chooks some ducks, geese and a host of wild birds which we encourage with lots of nectar rich flowers, and they seem to eat most of the garden pests. (We are the only garden for a couple of miles (surrounded by farmland))

ooohlaa (author)buck22172015-08-17

Lid not really airtight so they find their way; burning off the seed heads sounds like a good idea. I will torch them and throw the rest into the compost. Thanx to all for all the good comments. Very helpful.

ac-dc (author)ooohlaa2015-08-16

It will kill larvae if you put some acid in it to lower pH enough. Use vinegar or another plant compatible type, then when it comes time to use as fertilizer you want to bring the pH back to nearly neutral by adding some minerals, for example magnesium or esp. calcium and agitating for a short while.

Just be aware that the resultant mineral salts are very rapidly absorbed, a super-fertilizer that can kill a plant if used excessively but the same is true without any of this, just the water alone is too nutrient dense to use without dilution.

Berkana (author)2015-08-17

The deep rooted stuff is great! Those weeds pull up minerals from the sub-soil layers that are not always accessible to vegetables plants.

gaprilday (author)2015-08-17

Nice instructable. You might A few tablespoons of salad oil on the top of the water will kill the mosquito larvae. Perhaps Dawn dish liquid would too, like fly traps we make for the kitchen. I had some weeds in a bucket from weeding the garden, they just filled with rain and I used the 'sludge' a couple of months later to fertilize my brother's sunflowers and gladiolas. He won 1st place with the gladiolas, but look at these sunflowers. I thought they were just great seeds, but now I think better. More weeds, more rain, more sludge.

buck2217 (author)gaprilday2015-08-17

Brilliant sunflowers, they were my dads favorite. I think the best thing about this is it is something for nothing - not even a lot of effort, and getting rid of something that would otherwise be a problem.

kimberley.vaughan.7 (author)2015-08-17

Thank you! At last a good use for weeds! yay!!!

You're welcome!

FrankL3 (author)2015-08-17

your compost mosquito problem will be minimized if you try black plastic cover it will bake them, also adding a few chickens will dramatically cut your bug population down, I also live in Fl. and have found that just a couple hens will really wipe out a lot of bugs and they turn the soil big time. Just don't let them find out that penuts grow in your garden or you will have extreme digging!

buck2217 (author)FrankL32015-08-17

We have about 20 chooks (brown shavers and Bantams) and now have no slugs, snails, very few crickets and the flies and gnats are almost gone, they have learnt not to eat bees and wasps!!

lynne.findley.1 (author)2015-08-16

I cannot think any weed seed could survive six months of this. Great idea. I took the master gardener class here in WA. state and they told us to either do this with weeds, throw them in the garbage or burn them. The only hitch in my get-along is to try to get a barral half this size for my little garden. Thanks. :)

buck2217 (author)lynne.findley.12015-08-16

Try your local recycling centre, or you could do it in a plastic packing crate (like the ones they sell at places like Repco (or here in NZ the Warehouse) or try Bunnings

lynne.findley.1 (author)buck22172015-08-16

I was thinking two five gallon buckets too. :)

buck2217 (author)lynne.findley.12015-08-16

That would work

Try a 5 gallon bucket with a lid, or maybe 2 buckets.

I was thinking two five gallon buckets too. :)

sandres374 (author)2015-08-16

I've heard that if you have burned the seed heads etc., you can apply the ashes to the soil because the ash still has some usable minerals.

richard.snodgrass1 (author)2015-08-16

thanks for the info. never heard this before. I LOVE THIS SITE, IT'S SO INFORMATIVE AND CREATIVE.

Thanks I love it on here, even if you never make anything the ideas are great. mind you there is the occasional one that is WAY out of my league. They usually start with something like "first take your CNC machine and Carbon laser, and using the plutonium you harvested from your fast breeder reactor .............."

rwood10 (author)2015-08-16

I think you are underestimating the power if the weeds seeds. I would just make sure you cut off the weed heads.. Seeds can lay dormant for up to 10 years and you can't drown them. You may want to put this concoction in the sun it takes 30 days of exposure to temperatures of 145 degrees or more to kill seeds from tougher weed species. I learned when I became a master gardener. But this is a wonderful idea. Thanks.

buck2217 (author)rwood102015-08-16

Thanks I generally burn all the seedy weeds but will bear in mind. I try to dig up weeds before they go to seed, when we first moved in (7 years ago) we basically had 4 acres of thistle! I dug them all out (some 500+ barrow loads) and burnt them The following years I probably had 50 barrow loads, and this year probably 2 (mostly small ones which I sprayed)

Jack Rodgers (author)buck22172015-08-16

Recently there was a page somewhere on goat herds for hire. Hundreds of goats descend on acerage and eat all the weeds. Then they are hereded to the next area.

buck2217 (author)Jack Rodgers2015-08-16

I have sheep and they eat a fair amount of the weeds - goats are escape artists and will eat everything just about, however if there is something nicer than weeds they will go for that first!!

blenderbender (author)rwood102015-08-16

I think the key here is to harvest weeds before they go to seed...... some folks actually get around to that :)

buck2217 (author)blenderbender2015-08-16

Better adjust my halo then!!

ManifoldSky (author)rwood102015-08-16

Seeds from almost all weed species will fully decompose in the anaerobic conditions of a total submersion digested is a few weeks.

nflemming2004 (author)rwood102015-08-16

Wouldn't the anaerobic decomposition processes eat through the seeds over the 4-6 month period mentioned?

ac-dc (author)nflemming20042015-08-16

If it is viable seed then submerged in acidic (a byproduct of the bacteria breakdown process) solution it will have tried to sprout and been killed in a matter of days for a number of reasons I posted previously in this thread.

michael47362 (author)rwood102015-08-16

By running the seed pods through a grinder, they will become a great part of the mix.

About This Instructable




Bio: I am a Marine Engineer in the RNZN (39 years done in various navies) and am looking forward to retirement!!! so I can do more ... More »
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