A Simple Recipe for Fertiliser Tea

This is a very simple fertiliser tea recipe which all plants I have used it on have responded very well to. It uses wild plants which are generally abundant throughout Europe, although I am not sure about the rest of the world; you’ll have to look around for yourself.

The ratio I used here is approximately 1kg of plants to 10 litres of water.

Since you may not have scales handy in your garden it might be easier to measure by eye. Two large buckets stuffed full of plants = around 1kg. Don’t worry too much about this, though; it doesn’t have to be exact!

Ingredients

Entire plants (chopped without roots):

  • Comfrey
  • Dandelion
  • Plantain

Plus water.

Materials

  • Large bucket (any material except metal, which may rust)
  • Garden shears
  • Piece of fabric
  • Another large bucket (optional)
  • Screen with frame (optional)

Method

Place the plants in the largest bucket you have. I use what in Britain is known as a ‘trug’, which usually has around a 40 litre capacity. Any material is fine, although metal is inadvisable as you will be leaving the tea to soak over a number of weeks so you will likely want to avoid rust.

Using garden shears, stand or kneel over the bucket and chop the plants finely. It doesn’t have to be as smooth as a pesto sauce, but get them all into nice small bits to help accelerate the succession of bacteria getting in there to make lovely, rich tea.

Add around 10 litres of water for every kg of plants.

Stir with large stick.

Cover with some kind of material, so that the air can get to it but to avoid insects and debris from falling in.

Leave for at least 1 week and up to four weeks.

After this time, try lifting up the piece of material. Is the smell which greets you strongly reminiscent of cow dung? If so, congratulations: your fertiliser tea has been successful. Now you can begin to use the fertiliser tea on your plants.

Here if you have it, you can take your other large bucket and place the screen on top. Then, with someone’s help (be careful of those backs, people!) take the fertiliser tea-filled bucket and pour its contents through the screen into the other bucket. Now you have only the liquid and you can take what you need from the second bucket.

If you don’t have a second bucket, it is still possible to fill up a bottle by simply dunking it in. The only minor setback here is bits of plants possibly getting stuck in your watering can.

Make sure you dilute the fertiliser tea at least 10 times: it’s powerful stuff! So for a 10-litre watering can, add only 1 litre of fertiliser tea. You can use it on any plants, from new seedlings to trees. Watering with the tea in the evening is advised, to avoid burning leaves.

Once you have completed using the fertiliser tea for one day, if you still have some left you can re-mix the liquid with the plants (if necessary) and add in again the same amount of water that you took out.
Stir again.

It is possible to keep taking fertiliser tea out and re-diluting it repeatedly. When the smell becomes noticeably less cowpat-like, it is probably weak enough to warrant making new fertiliser tea.

Other information

Unsuccessful tea

If, when you lift the material after leaving the tea, your liquid does not smell of cow dung, it could be because the mixture has gone anaerobic — i.e. not enough oxygen has been able to reach the bacteria and so they have died. In this case the water will be black.

If so, try repeating and making sure that the material which you use for the cover is breathable, or that you leave a gap for the air to get in. Also try stirring the mixture more often.

Alternative plants

If you have cast your eye around your vicinity and not been able to spot the plants used in this recipe, have no fear. There are many other species which you can use, and although I have not personally tried them here are some recommendations:

  • Chamomile
  • Elder
  • Garlic
  • Holly Oak leaves
  • Horsetail
  • Lavender
  • Marigold
  • Nettle
  • Oak leaves
  • Onion
  • Walnut leaves (caution is advised with this one – see Hemenway’s comments on allelopaths) (1)
  • Yarrow

References:

  1. Hemenway, Toby, 2009. Gaia’s Garden: A Guide to Home-Scale Permaculture, Chapter 9: Designing Garden Guilds. Chelsea Green Publishing, Vermont.

Further Reading:

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6 thoughts on “A Simple Recipe for Fertiliser Tea

  1. This is called weed tea or some other kind of plant tea, there’s no compost involved. I’d expect the water to be anaerobic whether it smells like a cow pat or something else. Any strong smell is produced by the gasses made by anaerobic bacteria.

  2. Hmmmmm. Most people making comfrey teas where the leaves are combined with water note a manure smell. If the brew is anaerobic, is that a bad thing? I know it is for compost teas but is it also for plant/herbal teas. In fact, many references say that the tea is ready when it smells.

  3. Comfrey tea smells like rotten cucumber to me. I’ve left them 1,2,3,4,6 weeks in separate containers. Applying the tea after those several week intervals had the earthworms coming to the surface to eat of the ‘sludge’ I like to call it. Redworms seem to absolutely love it. They bathe in it, crawl through it, eat of it. :)

  4. There’s a science to the recipe for aerated compost teas. If you add too much food it can be driven anaerobic by the biological activity, even when you are pumping air into it. Temperature and altitude also have an effect. If you can’t measure dissolved oxygen a 40-400x microscope allows you to see the kinds of organisms in the brew. A large number of ciliates, which feed on anaerobic bacteria indicate the brew went anaerobic – it’s happened to me. I really wonder if the author of that Gardenweb article has done that – he is adding a lot of food to a 5 gallon brew!

    I steer clear of anaerobic teas, but perhaps on a small scale they are mostly harmless. I suspect that if you have an aerobic soil with a healthy population of predators, most of the disease causing anaerobic organisms in them will be consumed (by worms and such), and corrosive compounds (alcohol, organic acids) diluted and broken down. I just don’t see much point risking it though. It’s really disgusting stuff to deal with, you lose a lot of nutrition to the atmosphere (N, P & S), and the nutrition and aerobic biology could be delivered by other means, such as hot or worm compost turned into compost extract, aerated tea, or just top dressed for the microbes to distrubute. If the soil ecology is booming the microbes will seek out and turn mineral particles into soluble nutrition for the plant, saving you from spoon feeding them.

    As far as limitations to growth of a plant goes, it’s probably water, nitrogen, and then diversity of (aerobic) biology. A lot of the nitrogen is lost to ammonia gas in anaerobic teas, so you’re mostly getting benefit from watering and maybe a small benefit from cycling nitrogen and nutrients around the plant due to increased activity of predators. It’d be nice to quantify it in some controlled experiments.

  5. I suspect that most people aren’t aware of the science behind the brew. It seems to be a bit confused if Yahoo’s Compost Tea group is any indication. One wonders why so many of the plant tea articles don’t raise the possibility that the smell might mean that the tea has gone anaerobic. It’s easy and fairly cheap to make an aerated unit, either vortex or bubbler, as long as the pump is powerful enough and the design is kept simple.

    I’d love to have 40-400x microscope and the training to go with it but I don’t really have the money to spend so I’ll continue to let results or lack of guide me.

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