Thursday, 31 December 2015

Simple homemade natural fertiliser

Making a simple liquid fertiliser at home is a great way to maintain the fertility of the soil and directly feed the plants with a natural fertiliser that has readily accessible nutrients - easy for the plants to integrate. 

My favourite brew is comfrey tea.  Comfrey is a well-balanced natural fertiliser that really helps to boost plant health and vitality. All you need is comfrey, water and a bucket with a lid - that's it.

I grow comfrey, Symphytum officinale, in many parts of my garden - particularly around the chickens and compost systems, under fruit trees and around the edges of the garden.

Simple Comfrey Tea Method

This is the simplest method I know to make comfrey tea. I have a large barrel of it at home and encourage each of the community gardens and school gardens I work with to have one too.
  1. Harvest comfrey leaves and roughly chop (the smaller the piece, the more surface area and the more quickly the leaves break down)
  2. Place comfrey leaves in a large bucket or barrel with a fitted lid (often I use a large plastic garbage bin).
  3. Add water - just enough to cover the leaves (may need to put rock on leaves to keep under water).
  4. Stir regularly over next 6 weeks (keep a stake near the barrel).
  5. Water vegetables every week or two with this brew . I simply scoop a bucket in and fill a watering can with one part of comfrey tea to 10 parts of water.

Bubbling Liquid Fertiliser

When you first make the tea, you will notice that after a couple of days, bubbles will appear when you give it a stir indicating that the leaves are beginning to ferment. After a few weeks it can be used, but I prefer to leave it for six weeks before spreading it out - it will be stronger and will go further.  As different seasons and climatic regions have different timings for the fermentation of the leaves, I usually look instead at the change in colour - I like to wait for it to turns from a yellow/green colour to a brown colour. 

The key thing to know is that at the initial bubbly stage, the brew really stinks!  It is important - no, imperative - to have a tight-fitting lid. Both you and your neighbours will appreciate this. Don't worry, after the fermentation stops the smell diminishes.

Comfrey and weed tea fermenting in a large barrel above my vegetable garden.

Using a bag

Some people suggest putting the comfrey leaves in a hessian bag, stocking or something else that is permeable. This is particularly useful if you want to have a tap at the bottom - it prevents the tap from becoming clogged, although you could also install the tap several inches from the bottom (above the sludge line). Since I scoop my comfrey tea from the top I don't worry about the bag.

Adding weeds and other ingredients

In addition to comfrey there are many leaves from the garden that are beneficial to add for example yarrow, nettle and chickweed. 

I most often add weeds from the garden - plants with seeds I do not want to add to the compost. I love making all sorts of composts, but I am not a master composter who ensures my compost stays above 55 degrees celsius (130F), so it is likely that the seeds will still be viable and as the compost is spread out, the seeds will be redistributed through the garden. In the liquid fertiliser however, the fermentation process breaks down the seed, and the weed plant has been turned from a being part of the problem into being part of the solution. 

Using the comfrey tea sludge

As the comfrey liquid is drained off, an accumulation of leaf sludge remains at the bottom of the barrel. This is a great resource - for example, it is a compost activator, can be added as a soil activator in a no-dig garden, or dug into a trench below potatoes.

Liquid Fertiliser for Balconies and Small Yards

A small garden or balcony can make a mini-version to feed potted plants. Again, make sure the container has a highly fitting lid, like on a nappy bucket, to contain smell while it ferments. 


  1. Good morning, I was given a piece of comfrey by Rhonda (down to earth) a while ago and it has gone mad. I put it in a pot as I don't have a large garden. I have had 2 goes at making comfrey tea for fertiliser and you are so right, it stinks to high heaven. I will try your method of leaving it for a longer brewing time! I also saw a while ago you used comfry in the eggy bake, i am a little hesitant to eat it as a leafy green. Is it ok to use in smaller quantities? Have a great day.

  2. Hello Fiona, One way I find to keep comfrey under control in a small garden is keep harvesting it. Once established, you can pull all the leaves off and use them in compost, mulch, no-dig gardening, liquid fertiliser...even mulch. It will regrow leaves quickly. The only reason it will spread is if you dig around the roots. If you have a plant somewhere you don't want, simply newspaper and mulch over the top. It is definitely preferably to have it in the ground as it is a deep nutrient cycler. It has really deep roots that seek out moisture, minerals and nutrients from deep down in the soil, bring this fertility to the surface. A plant grown in a pot can only benefit from the nutrients available in the soil medium used. I do eat a little bit of comfrey regularly - but only the little young leaves. You would need to consumer almost 20,000 large leaves over decades to reach the toxicity levels shown in the lab rats fed concentrated comfrey in the study that led to the ban of the therapeutic use of the concentrated form of the root. The leaf used as food was never the issue. We need to keep in mind that consuming any plant (or food) in such concentrations is not going to be good for us. Read Isabel Shippard's information about the research for more information

  3. Thanks Morag for the info, i think I will try and find a spot in the limited garden for the comfrey. Happy new year to you and yours!

  4. We use comfrey tea at Beelarong Community Farm as a fertiliser, it's magic stuff once you get over the pong. One of the ladies at the farm told me 'in the old days' comfrey was used, in the form of a poultice, to relieve bruising in the skin.

    1. That's great Jean. A traditional name was knit bone - used to help heal broken bones. I also love to make a salve from it to help with bruising and wounds - I'll write a post about this soon too. An earlier post explains how I made the comfrey oil - the base for the salve.

  5. Hi Morag, thanks so much. I will try this tea. It will be great for my fruit trees as well. I have a large garden but the soil in my vegie garden is not good, I can't get anything to grow, my tomatoes and capsicum did not grow at all. I have dug in cow and horse manure at the beginning of the season. I have put straw mulch on the top to stop the weeds and will not plant anything until I get the soil right. Any suggestions?

    1. Hi Antionette, Take a look at my latest post about how to create a no-dig garden. This methods has served me extremely well in turning around some disastrous soils, as well as improving OK ones. It's simple and quick, cheap and super-effective. I'm hoping to make a little video clip soon to make the method even clearer. Perhaps you might like to give it a go. Happy Gardening!

  6. Hi Morag,
    I've been meaning to make comfrey tea for a while, so your post has inspired me to get moving :)
    I was wondering, would it be suitable to add leaves which I have nipped off because they have powdery mildew? Or would that spread the problem?
    Thank you

    1. Hi Katy - that's great!
      I am not sure about this. I know that watering plants with comfrey tea helps to prevent powdery mildew, but I am not sure if putting the leaves in the mix would be OK. I think it could be, but let me delve further. I'll come back with a definitive answer I hope. In the meantime, if anyone else reading this has some information about this, please post a comment here. We'd love to hear.

  7. Thanks for this Morag. We have comfrey growing and I will be making this. Our other concoction centres around horse manure and kelp.

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  9. I cannot begin to express my gratitude for your YouTube, Newsletter and Blog. I live in Alabama, USA and have learned more about permaculture from you than I have from others here. I have comfrey growing and had just heard about "knitbone" characteristics and then you have given me more information.
    Although I am in Planting Zone 8 I can still use many of your recommended plants and shrubs.
    Qst: I have read about the edible parts of the pumpkin. Does this info include yellow crookneck and zucchini squash? Is there a site to check this kind of information?
    Do you deal with fire ants in your location?