Making Liquid Fertilizer From Weeds





Introduction: Making Liquid Fertilizer From Weeds

About: 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 messing about with tools

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

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

Top up the barrel with weeds and fill with water

Cover and leave for 2 weeks minimum

Step 3: 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



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86 Discussions

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

1 reply

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.

1 reply

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

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.

2 replies

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.

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

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!

1 reply

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

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

1 reply

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

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.

1 reply

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!

6 replies

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

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.

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...

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.

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