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Fermented tea, using weeds to make fabulous organic treatments

Wooden bucket used to prepare fermented weed tea in.

Fermented tea from weeds is an effective and environment-friendly resource to fight most insects, pests and plant diseases.

Here are the steps to prepare them and a summary of their specific advantages and characteristics.

Take note that generally, fermented tea is best used as a preventive treatment, and often cannot treat a disease once it has contaminated a plant.

Maceration and fermentation

Over time, gardeners learned that most weeds would make great fermented weed tea. In effect, the basic recipe is always very similar, but certain weeds have different steps.

Here are the basic steps to make weed tea

  • Collect and chop the weeds. Doesn’t need to be very fine, the goal is to make it easy to stash them into the container.
  • Use about 10 times more water than you do fresh plant material, 1 kg for 10 liters in the metric system. For the imperial system, macerate 1 pound of leaves in 5 quarts water, but 1 lb to a gallon is also effective (it’s a broad rule of thumb).
  • Wait for one or two weeks. During this time, mix daily.
  • After leaves break down into a black slurry, filter the plant parts out and keep the liquid.
  • This is the final product. Store in bottles, jugs or jars. Plastic and glass are fine, but don’t use metal.
  • To use, dilute this very rich solution. For example, pour 1 quart of it into 9 quarts water (1 liter for 9 liters). This makes a 10% solution that can be sprayed without “burning” plants or seedlings.

Different weed teas have slightly different recipes.

Most common types of weed tea

Although it’s possible to use almost any kind of weed to prepare nutritious weed tea, some weeds appear more often than others in traditional recipes. Each one has different properties and helps deal with different problems.

Stinging nettle weed tea – boosts the plant’s immune system, especially against different types of fungus. Aphids are repelled by it.

Rhubarb fermented tea – quick to prepare. Mostly used against insects like allium leaf-mining flies and aphids.

Garlic (decoction) – effective to prevent fungal disease. Fends off aphids, thrips, mites and ticks.

There are more, of course, such as fermented horsetail or the well-known comfrey weed tea.

Comment below to ask if a local weed that’s driving you crazy might be converted to a useful fermented weed tea!

Additional ingredients and mixing weeds

Making fermented weed tea from different weeds

It’s perfectly possible to make batches of fermented weed tea by mixing material from different plants together. You’ll have the benefits of each.

Fans of the process have a continually fermenting pot or barrel somewhere in their garden where they keep adding plant material as they weed the garden.

Crucial to the success of each fermented tea batch

Water – must be as close as possible to natural rainwater. Avoid tap water if possible. If you must use it, let it sit for at least an hour, at best a whole day, without a lid. Chemicals that keep it safe for drinking, like chlorine, will evaporate.

Trigger – usually enough micro-organisms are present on the leaves themselves to launch the fermentation. These are called epiphyte organisms, meaning they live on the plant without parasiting it.

  • If ever it takes more than three or four days to start fermenting, you can add fermenting triggers to the mix.
  • if you’re a fan of kombucha, you can add a slab of mother to the mix.
  • keep some degraded plant material from your previous batch (whatever the weed), or start a new batch from the end of the previous one.
  • a handful of ripe compost, vermicompost, or animal manure also does the trick.
  • from the kitchen, you can add a live yoghurt or a spoonful of curdled milk.

Timing – you can harvest the weeds anytime, but fermentation starts fastest and nutrient conversion is highest when you follow these tips:

  • set your weeds to ferment immediately after picking them. Don’t let them dry out.
  • harvest your weeds early morning to collect the guttation fluid. Guttant is usually chock full of nutrients and trigger micro-organisms.

Other ingredients to make the fermented tea more potent

  • Coffee grounds – It’s also possible to use specific food scraps from the house, such as coffee grounds. Spent tea leaves are also good. Simply add them to the recipe and the grounds will leach their nutrients into the fermented tea.
  • Sugar – it may sound surprising, but sugar has been proven to help plants out. For example, birch trees recover from transplant shock much better with a mixture of sweetened water. Plain sugar will do, but you can also use molasses. Try to find non-treated materials (sugar cane molasses, etc) because additives like sulfur usually try to kill or control useful micro-organisms.
  • Air bubble device – an old bubbler from an abandoned fish tank will create convection currents. Materials will mix out better and you won’t need to stir as often. It will prevent  fermentation from turning into rot.

Last notes on fermented organic fertilizers & treatments

Put a cover on your fermenting weed tea to keep insects out and smells in. This will keep mosquitoes from multiplying and small animals from falling in.

Usually degraded plant materials are filtered out. This makes it easier for sprayers and watering cans. But you can keep them to trigger the next batch, enrich your compost or mulch needy trees with it!

Advantages of fermented tea over chemical products

The most important advantage is that this tea is “alive” as opposed to “sterile” products.

It creates and strengthens the ecosystem. Consider your plant as part of a community. Fermented teas try to build the community up and increase biodiversity. Chemicals are more single-minded about things.


Insight Chemical products Fermented tea
Mode of action Harms the pests Empowers the plant
Effect on plant Weakens the plant Strengthens immunity
Effect on beneficial animals Eliminates them, too Usually not impacted
Effect on soil Slowly sterilizes it Makes it richer
Effect on water Leaches to the watertable None
Effect on humans Toxic warnings
when handled
Depends on weed used,
some can even be drunk
Repeatability Repeat application at
each new infection.
Immunity increases,
need to repeat decreases
Long-term effect Pest develops resistance
to treatment
Plant develops resistance
to pest
Battlecry Kill them all! Crowd the invaders out!


There are a few disadvantages, which are mostly related to how we organize our work. Indeed, chemical products are just a click away online, or a short drive to the garden center. They’re usually immediately effective and make for faster treatment.

Why does fermented tea work?

Plants never exist “alone” in their environment. They are surrounded by living creatures. We’re familiar with most insects and caterpillars, but there are also microscopic members in this community.

Plants are part of a living ecosystem

Epiphyte micro-organisms are those tiny germs, fungus, yeasts, molds and mites that live on the surface of plants. They cover leaves, stems and trunks.

Mychorrhizae are underground fungi that work with plants together to extract nutrients from decaying material and available minerals.

Fermented teas develop lots of yeasts and beneficial germs. Spraying on both leaves and soil helps. They make the plant’s work easier by:

  • providing nutrients,
  • strengthening the number and diversity of micro-organisms,
  • crowding out harmful germs.

The technical term for this is “infection antagonists”, meaning they fight infection together with the plant.

In a way, one can say “it brings out the best in all of us”, since even us humans are made more aware of the intricate beauty of nature!

Science proves effectiveness of beneficial yeasts and bacteria

In an experiment involving beneficial yeast and bacteria on tomato plants, a significant reduction in infection took place. This was conducted on Septoria fungus, a common cause of leaf spot.

Infections dropped by 20 to 80 % compared to untreated specimens. Results varied depending on the yeast and bacteria used, but every case showed an improvement against the control sample.

When is fermented weed tea useful?

Whenever plants need nourishment or are under stress, fermented weed tea can help.

With this in mind, it’s worth working these natural solutions into your usual gardening routine. By and large, weed tea will work wonders for the garden, your wallet, and everybody’s health, including the planet’s!

Read also:

Smart tip about making weed tea

When preparing it, find a spot that’s a bit far off, because it sometimes releases quite a stench! Also, place a lid (not an airtight one), it’ll help lock the smell in.

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  • Simone White wrote on 30 April 2023 at 22 h 11 min

    Love what you’re sharing about biodiversity and sustainable gardening. We live in northwest CT and there’s a ton of mugwort growing, it’s considered a serious invasive here. I know it’s good for humans as a tea, bath and tincture. I figure it must be good as a garden tea, do you know anything about it?

    • Gaspard wrote on 12 May 2023 at 12 h 21 min

      Hi Simone, mugwort is indeed a very interesting plant for fermented tea. It’s said to have insecticidal properties, meaning it would certainly work well to get rid of aphids and mites and thrips and similar small insect pests. There hasn’t been much research on it specifically, though – a few sources cite that it might have anti-growth effects on some plants. This would make it interesting for nurseries: sometimes they have to slow growth down on their plants in order to better time them to the market. Slower growth also makes shrubs more dense and lush, especially if paired with frequent pruning.

      All in all a very interesting option – I do wish I had more research and experience to rely on! It doesn’t grow in my parts so I can’t test it out myself.

      Biodiversity is truly an amazing find: of course, you still get pests, but never enough to really kill off entire crops because there’s always some other critter gobbling the pests up!

      • Simone White wrote on 12 May 2023 at 14 h 58 min

        Thank you, Gaspard. That is fascinating information. I hadn’t thought about the properties of the living mugwort continuing to the tea. (I’ve read that when it’s growing it emits a toxin that inhibits growth of other plants around it). But using it for intentional slow growth is interesting! Maybe it would be good to spray it on our grass. If I can get it together to do a controlled experiment I will report back. :-))

      • Gaspard wrote on 20 May 2023 at 10 h 11 min

        Great idea!

  • Andrew C wrote on 20 November 2020 at 22 h 15 min

    You’ve got “macerate 1 pound of leaves in 10 quarts water (1 kg for 10 liters)”. Obviously, while a quart is just about a liter, a pound is not just about a kilo, so this is off. Since the rule of thumb is about 10x water:plant material, and that’d obviously be weight/weight (as vol/vol would be arbitrary and meaningless), it should be about 1 lb to 5 quarts (more accurately 4.8 quarts but I doubt the rule of thumb needs to be that stringent, given the weed species and “strength” itself is random anyhow!) Cheers….

    • Gaspard wrote on 21 November 2020 at 19 h 46 min

      Oh my, thank you so much! I try to make it easier for readers by including both metric and imperial, but sometimes I get mixed up in the conversion. Of course, one pound is nearer to half a kg, so as you wrote, it should read 1 lb to 5 quarts. Thanks for signaling the mishap, I’ll get the article in line immediately.