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.
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.
Different weed teas have slightly different recipes.
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!
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.
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.
Timing – you can harvest the weeds anytime, but fermentation starts fastest and nutrient conversion is highest when you follow these tips:
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!
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.
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.
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:
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!
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.
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!
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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.
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?
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!
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. :-))
Great idea!
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….
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.