Weed tea – a free natural fermented fertiliser
Tuesday, 15 September 2015
A few weeks ago I wrote about making herbal tea from foraged weeds. I'm making weed tea again - but I won't be drinking this batch. This brew is for the garden.
In a couple of weeks' time I'll have bucketfuls of stinky liquid fertiliser, rich in minerals and microbes, ready to boost the productivity and resilience of my garden.
Turning weeds into nutrient-rich liquid fertiliser is a great way to use a resource that may have otherwise gone to waste.
Basically, weed tea is made by fermenting weeds in a bucket of water.
The fermentation process creates a liquid fertiliser rich in soluble nutrients and a diversity of beneficial microbes.
The result is not only a boost in productivity but also increased resistance to disease and insects.
What weeds can be used?
I'm making my current brew using Stinging Nettle and Fireweed, which are abundant in my neighbourhood at the moment. But any weed will do. Other weeds I've heard of being used include Clover, Chickweed, Lantana and Scotch Broom.
Fleshy, deep-rooted weeds like Dandelion and Dock are especially good because their roots mine valuable nutrients from deep in the ground.
Weed tea is also a great way to use grass clippings or weeds that you prefer not to compost for fear of spreading weed seeds. For example, I've been tossing Fireweed into a large sealed bucket. A best practice management guide for the control of fireweed suggests it should be placed in a sealed bag and burnt or buried. By first making weed tea, I'm extracting all the nutrients before disposal.
I'm being cautious - and only use edible weeds (e.g. Nettle, Clover, Chickweed, Dandelion and Dock) on edible plants. I use tea from toxic plants (e.g. Fireweed & Lantana) on ornamental plants.
How to make weed tea
The first step in making weed tea is to fill a bucket with weeds. A plastic bucket with a lid is ideal.
Pack the weeds down as tight as possible.
Continue filling and packing until your bucket is around two-thirds full of tightly packed weeds.
Your tea will naturally be colonised by beneficial microbes but you can speed up the process by inoculating it with preservative-free fermented foods such as sourdough starter, sauerkraut, kefir, yoghurt or organic beer or wine.
I added a generous spoon of home-made sauerkraut.
Fill your bucket of weeds with water. If using chlorinated town water, first leave a bucket of water in the sunlight for at least a day so that any chlorine can evaporate.
Hold weeds under the water surface using a brick or large rock, then place a loose lid or cover on the bucket.
Make sure it’s not air-tight as the fermentation process releases carbon dioxide – and I'm sure nobody wants an exploding bucket of smelly liquid fertiliser.
Leave your bucket of tea somewhere warm to ferment for a week or two.
Happy bubbling fermenting weed tea.
How to use weed tea
Before using, you can strain your weed tea through a piece of cloth or a pair of stockings. Straining ensures you don't disperse weed seeds or clog the nozzle of your watering can.
Or, if you aren't concerned about spreading weed seeds or aren't using a nozzle on your watering can, you can simply bucket out the fermented liquid as you need it.
**CAUTION** Try not to spill any weed tea on your hands or clothing. Especially if you are about to run out the door for school pick up. Trust me - it smells REALLY horrible. And the smell lingers - even after repeatedly washing hands with soap and water.
Dilute your strained tea until it is the colour of a weak black or herbal tea.
Dilution rate will vary between batches and will be influenced by the type and quantity of weeds used. Around 1:10 should be a good start.
Over-diluting is far better than not diluting enough, as strong fertiliser can burn young roots or shoots.
Your diluted weed tea can then be poured over the root zone of growing plants.
Don’t apply to vegetables about to be harvested as I'm sure (based on its smell) it doesn't taste good.
Diluted again to half-strength, it also makes a great fertiliser for indoor plants and seedlings.
Originally published in the Newcastle Herald Monday 14th September 2015.